Run off with extremely comfortable wool coat (6)
I believe the answer is:
fleece
'wool coat' is the definition.
(I've seen this before)
'run off with extremely comfortable' is the wordplay.
'run off' becomes 'flee' (I've seen this before).
'with' is a charade indicator (letters next to each other).
'extremely' says to hollow out the word (remove centre letters) (only the extremes of the word are used).
'comfortable' with its middle removed is 'ce'.
'flee'+'ce'='FLEECE'
(Other definitions for fleece that I've seen before include "Defraud in woolly way" , "thermal garment" , "A sheep's wool coating" , "Covering" , "Swindle; sheep's coat" .)