Gain in credit and comfort (8)
I believe the answer is:
increase
'gain' is the definition.
(thesaurus)
'in credit and comfort' is the wordplay.
'credit' becomes 'cr'.
'and' says to put letters next to each other.
'comfort' becomes 'ease' (easing is a kind of comforting).
'in'+'cr'+'ease'='INCREASE'
(Other definitions for increase that I've seen before include "Make larger in a sincere way" , "Increment" , "Amplification" , "Add, make bigger" , "Augment or enlarge (8)." .)