Not fighting growing old (7,2)
I believe the answer is:
getting on
'old' is the definition.
(thesaurus)
'not fighting growing' is the wordplay.
I cannot really understand how this works, but
'not' could be 'o' (I've seen this in other clues) and 'o' is found within the answer.
'growing' could be 'getting' ('get' can be a synonym of 'grow') and 'getting' is present in the answer.
A single letter 'n' remains which might be clued in a way I don't understand.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for getting on that I've seen before include "Embarking" , "no longer young" , "Enjoying friendly relations" , "Elderly; succeeding" , "as a boarder > in later years?" .)