No collar brought back for tree (6)
I believe the answer is:
banyan
'for tree' is the definition.
(banyan tree is a kind of tree)
'no collar brought back' is the wordplay.
'no' becomes 'nay' (archaic form of 'no').
'collar' becomes 'nab' (both can mean to catch a person).
'brought back' says the letters should be written backwards.
'nay'+'nab'='naynab'
'naynab' back-to-front is 'BANYAN'.
(Other definitions for banyan that I've seen before include "Fig tree with aerial roots" , "one that does give a fig" , "Indian fig tree with self-rooting branches" , "Any ban for an Indian tree" , "Crush underfoot" .)