Topless beekeeper going round trail: his ideas aren't fresh! (10)
I believe the answer is:
plagiarist
'his ideas aren't fresh' is the definition.
'topless beekeeper going round trail' is the wordplay.
'topless' means to remove the first letter.
'beekeeper' becomes 'apiarist' (synonyms).
'going round' indicates putting letters inside.
'trail' becomes 'lag' (both can mean to go behind).
'apiarist' with its first letter taken off is 'piarist'.
'piarist' placed around 'lag' is 'PLAGIARIST'.
(Other definitions for plagiarist that I've seen before include "Literary pirate" , "One copying" , "sort of thief" , "Stealer of others' work" .)