Tap a spirit after difficult start (4)
I believe the answer is:
drum
'tap' is the definition.
(I've seen this before)
'a spirit after difficult start' is the wordplay.
'a spirit' becomes 'rum' (alcoholic spirit).
'after' means one lot of letters go next to another.
'start' suggests taking the first letters.
The first letter of 'difficult' is 'd'.
'rum' after 'd' is 'DRUM'.
(Other definitions for drum that I've seen before include "See 18" , "nightclub" , "Percussion instrument" , "Mus. instrument; container" , "Thing to be beaten - but not as a container!" .)