Accomplished line inspiring old man (7)
I believe the answer is:
capable
'accomplished' is the definition.
(thesaurus)
'line inspiring old man' is the wordplay.
'line' becomes 'cable' (cable is a kind of line).
'inspiring' means one lot of letters goes inside another.
'old man' becomes 'pa' (both can mean father).
'cable' placed around 'pa' is 'CAPABLE'.
(Other definitions for capable that I've seen before include "qualified" , "'Clever, able (7)'" , "Competent, having a certain ability" , "Able, competent" , "Able, proficient" .)