Nip of absinthe occasionally? (4)
I believe the answer is:
bite
'nip' is the definition.
(I know that nip is a kind of bite)
'absinthe occasionally?' is the wordplay.
'occasionally?' means one should take alternating letters (letters taken at regular intervals or occasions).
The alternate letters of 'absinthe' are 'BITE'.
'of' is the link.
(Other definitions for bite that I've seen before include "Grip; take effect" , "Take effect; snack" , "(Of fish) take the bait" , "Clamp down teeth" , "Take bait; sting" .)