Compound formed from an alcohol and an acid (5)
I believe the answer is:
ester
'compound formed from an alcohol and an acid' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for ester that I've seen before include "Reset (anag.)" , "Compound formed from acid and alcohol" , "radical" , "Fat" , "Compound; trees (anag.)" .)