Squirrel’s tree behind road (5)
I believe the answer is:
stash
'squirrel's' is the definition.
(thesaurus)
'tree behind road' is the wordplay.
'tree' becomes 'ash' (ash is a kind of tree).
'behind' says to put letters next to each other.
'road' becomes 'st'.
'ash' put after 'st' is 'STASH'.
(Other definitions for stash that I've seen before include "Secret store (colloq.)" , "(Illegal) hoard" , "drug store" , "Stow; secret store" , "Secret store of valuables" .)