Suitable for salesperson after retirement (6)
I believe the answer is:
proper
'suitable' is the definition.
(synonyms)
'for salesperson after retirement' is the wordplay.
'for' becomes 'pro' (as in being 'pro' something).
'salesperson' becomes 'rep' (sales rep).
'after retirement' says the letters should be written in reverse.
'rep' in reverse letter order is 'per'.
'pro'+'per'='PROPER'
(Other definitions for proper that I've seen before include "Genuine; correct" , "Suitable or appropriate" , "Appropriate description" , "Refined" , "Seemly" .)