Abandoned cat in tree beginning to eat biscuit (7)
I believe the answer is:
oatcake
'biscuit' is the definition.
(I've seen this before)
'abandoned cat in tree beginning to eat' is the wordplay.
'abandoned' indicates anagramming the letters (the original order is abandoned).
'in' means one lot of letters goes inside another.
'tree' becomes 'oak' (oak is a type of tree).
'beginning to' says to take the initial letters.
The initial letter of 'eat' is 'e'.
'cat' with letters rearranged gives 'atc'.
'atc' put into 'oak' is 'oatcak'.
'oatcak'+'e'='OATCAKE'
(Other definitions for oatcake that I've seen before include "Traditional Scottish biscuit" , "something like a biscuit" , "Traditional Scots biscuit" , "Variety of biscuit" , "Dry biscuit" .)