Tree berry occasionally for Clive (6)
I believe the answer is:
palmer
'occasionally for clive' is the definition.
I can't judge whether this definition defines the answer.
'tree berry' is the wordplay.
'tree' becomes 'palm' (palm is a kind of tree).
'berry' becomes 'er' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'palm'+'er'='PALMER'
Can you help me to learn more?
(Other definitions for palmer that I've seen before include "Bait this" , "old monk" , "Itinerant monk; fishing fly" .)