Many experts play that a response of 4NT to a four-level, minor-suit overcall is natural. Had North–South agreed to this treatment, and had
North bid 4NT instead of 5♦, I would not have a quiz hand as there are 10 top notrump tricks. North,
however, raised to 5♦, and now you are in a contract that needs 11 tricks.
In order to make this contract, you must avoid the loss of two club tricks, as you are destined to lose at least one spade trick.
Given that West has the ♣K in order to justify a first-seat, vulnerable opening bid (without the ♣K, and excluding the possibility that West has the ♠K Q J, West can have at most 10 HCP), your best shot is to ruff the opening lead, cash the ♦A J and lead a low club. If the stars are in complete alignment, West will play the jack! Now you have 11 sure tricks: seven diamonds, at least two clubs, and two major-suit aces. But this is matchpoints so you must think “overtrick.”
Win the ♣A, ruff another heart and lead another low club towards dummy’s 10–5–4. If West plays the king (he may have to if he started
with king–jack doubleton), you have three club tricks which means an overtrick. Also, if the ♣10 holds, discard the ♣Q on the ♥A and ruff a club. If clubs go 3–3, score up an overtrick as both of dummy’s spades go away, one on a long club and one on the ♥A.
Okay, back to the real world where the stars are seldom in alignment. Say the 10 loses to the jack and a spade comes back. Win the ace and lead another low club. If the king appears, you have 11 tricks: seven diamonds, two clubs and two major-suit aces. If the ♣K does not appear, win the ace, discard the ♣Q on the ♥A and ruff a club. If clubs are 3–3, you survive, as dummy’s long club is your 11th trick.
Given that West started with the ♣K, this line loses if East started with a singleton ♣J (highly unlikely), or a doubleton ♣J.