Backing current opinion introduced by fool (10)
I believe the answer is:
assistance
'backing' is the definition.
(thesaurus)
'current opinion introduced by fool' is the wordplay.
'current' becomes 'i' (symbol for electric current).
'opinion' becomes 'stance' (I've seen this in other clues).
'introduced by' says to put letters next to each other.
'fool' becomes 'ass' (ass is a kind of fool**).
'i'+'stance'='istance'
'istance' put after 'ass' is 'ASSISTANCE'.
(Other definitions for assistance that I've seen before include "Aid" , "Support" , "Help" .)