Keanu's John in Caithness town (4)

I believe the answer is:

wick

I'm a little stuck... Click here to teach me more about this clue!

'caithness town' is the definition.
(I know that Wick is a town)

I don't understand how the rest of the clue works.

(Other definitions for wick that I've seen before include "fishing port" , "Scots town; part of candle" , "One to light up" , "combustible drawer" , "a slow burner?" .)

I've seen this clue in The Sun.

Want a hint initially instead of a full solution? Install my app