Criticise expert answer - a universal cure (7)
I believe the answer is:
panacea
'a universal cure' is the definition.
(I've seen this before)
'criticise expert answer' is the wordplay.
'criticise' becomes 'pan' (informal term meaning to criticise heavily).
'expert' becomes 'ace' (ace can informally mean very good).
'answer' becomes 'a' (abbreviation eg in Q and A).
'pan'+'ace'+'a'='PANACEA'
(Other definitions for panacea that I've seen before include "that will cure anything" , "Cure for all ills" , "A cure for everything" , "comprehensive fix" , "Cure for all things" .)