Hide a holy man by a tree (5)
I believe the answer is:
stash
'hide' is the definition.
(I've seen this before)
'a holy man by a tree' is the wordplay.
'a holy man' becomes 'st' (abbreviation for saint).
'by' means one lot of letters go next to another.
'a tree' becomes 'ash' (ash is a kind of tree).
'st'+'ash'='STASH'
(Other definitions for stash that I've seen before include "Treasure trove" , "(Hidden store of) drugs" , "(Illegal) hoard" , "Secret hoard" , "Stow away" .)