Culture expert to call back con­clusively, nurseryman claims (10)

'culture expert' is the definition.

'to call back conclusively nurseryman claims' is the wordplay.
'conclusively' indicates one should take the final letters (the letter which concludes the word).
'nurseryman' becomes 'florist' (flowers may be grown in a nursery).
'claims' indicates putting letters inside.
The last letters of 'to call back' are 'olk'.
'olk' put into 'florist' is 'FOLKLORIST'.