Goes off to catch fish with smart retired PR person (4,6)
I believe the answer is:
spin doctor
'pr person' is the definition.
'goes off to catch fish with smart retired' is the wordplay.
'goes off' becomes 'rots'.
'to catch' is an insertion indicator.
'fish with' becomes 'cod' (cod is a kind of fish. I am not sure about the 'with' bit.**).
'smart' becomes 'nip' (both can mean a pain).
'retired' says the letters should be written in reverse.
'cod'+'nip'='codnip'
'rots' placed around 'codnip' is 'rotcodnips'.
'rotcodnips' back-to-front is 'SPIN-DOCTOR'.
(Other definitions for spin doctor that I've seen before include "Massager of news etc" , "Supposed PR expert" , "Government communicator" , "Public relations expert" , "spokesperson" .)