Head accepting very good viewpoint (7)
I believe the answer is:
opinion
'viewpoint' is the definition.
(thesaurus)
'head accepting very good' is the wordplay.
'head' becomes 'onion' (I've seen this before**).
'accepting' indicates putting letters inside.
'very good' becomes 'pi' (I've seen this in other clues).
'onion' placed around 'pi' is 'OPINION'.
(Other definitions for opinion that I've seen before include "Assessment" , "View, judgement" , "Estimation" , "impression" , "Unproved belief or view" .)