Prohibit going round any fig tree (6)
I believe the answer is:
banyan
'fig tree' is the definition.
(I know that Banyan is a type of fig tree)
'prohibit going round any' is the wordplay.
'prohibit' becomes 'ban' (banning is a kind of prohibiting).
'going round' means one lot of letters goes inside another (some letters go around others).
'ban' placed around 'any' is 'BANYAN'.
(Other definitions for banyan that I've seen before include "Indian fig tree with self-rooting branches" , "one that does give a fig" , "Multi-trunked Indian tree" , "plant" , "Fig tree with aerial roots" .)