Hole (for a coin?) (4)
I believe the answer is:
slot
'hole for a coin?' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for slot that I've seen before include "Long narrow aperture" , "Long narrow slit" , "Narrow opening, for cash say" , "Opening for coin or TV programme" , "Long narrow opening" .)