Bear on show gobbling very loudly with energy (6)
I believe the answer is:
affect
'bear on' is the definition.
(synonyms)
'show gobbling very loudly with energy' is the wordplay.
'show' becomes 'act' (act can mean a show or facade).
'gobbling' indicates putting letters inside.
'very loudly' becomes 'ff' (short for fortissimo, 'very loud' in music).
'with' says to put letters next to each other.
'energy' becomes 'e' (physics symbol as in E=mc2).
'ff'+'e'='ffe'
'act' enclosing 'ffe' is 'AFFECT'.
(Other definitions for affect that I've seen before include "Impact, have a bearing on" , "Assume" , "attack" , "Put on" , "Have impact on or arouse sadness in" .)