Loose horse stuck in cove (5)
I believe the answer is:
baggy
'loose' is the definition.
(I've seen this in another clue)
'horse stuck in cove' is the wordplay.
'horse' becomes 'gg' (geegee or GG is a childish term for a horse).
'stuck in' means one lot of letters goes inside another.
'cove' becomes 'bay' (both can mean a coastal inlet).
'gg' put within 'bay' is 'BAGGY'.
(Other definitions for baggy that I've seen before include "Bulging" , "(Of clothes) loose and hanging" , "Falling in loose folds" .)