Commercial traveller wasn't truthful when he answered (7)
I believe the answer is:
replied
'answered' is the definition.
('reply' can be a synonym of 'answer')
'commercial traveller wasn't truthful' is the wordplay.
'commercial traveller' becomes 'rep' (a travelling sales representative).
'wasn't truthful' becomes 'lied' (told a lie).
'rep'+'lied'='REPLIED'
'when he' acts as a link.
This may not be correct. Some or all of it may be part of another bit of the clue.
Can you help me to learn more?
(Other definitions for replied that I've seen before include "Answered back" , "came back" , "Responded" , "Gave answer" , "Wrote back" .)