Absolute fanatic chasing a drop of blackcurrant squash (9)
I believe the answer is:
butternut
'squash' is the definition.
(butternut squash is a kind of squash)
'absolute fanatic chasing a drop of blackcurrant' is the wordplay.
'absolute' becomes 'utter' ('utter' can be similar in meaning to 'absolute').
'fanatic' becomes 'nut' (I've seen this before).
'chasing' is a charade indicator (letters next to each other).
'a drop of' says to take the initial letters.
The first letter of 'blackcurrant' is 'b'.
'utter'+'nut'='utternut'
'utternut' after 'b' is 'BUTTERNUT'.
(Other definitions for butternut that I've seen before include "Variety of pumpkin" , "sort of a squash" , "Wood" , "species of tree" .)