Vicar obliged to hold tree (5)
I believe the answer is:
carob
'tree' is the definition.
(carob is a kind of tree)
'vicar obliged to hold' is the wordplay.
'to hold' indicates a hidden word (I've seen 'holding' mean this).
'CAROB' is hidden in the letters of 'vicar obliged'.
(Other definitions for carob that I've seen before include "St John's bread" , "Locust tree" , "Evergreen tree with edible pods" , "Arabian tree with brownish-purple pods" , "Tree yielding chocolate substitute" .)