The old man exploits gaps in conversation? (6)
I believe the answer is:
pauses
'gaps in conversation?' is the definition.
(breaks or gaps in conversation)
'the old man exploits' is the wordplay.
'the old man' becomes 'pa' (both can mean someone's father).
'exploits' becomes 'uses' (use is a kind of exploit).
'pa'+'uses'='PAUSES'
(Other definitions for pauses that I've seen before include "Temporary halts" , "Temporary suspensions" , "Takes a short break" , "Short silences" , "Short breaks in business" .)