Bouncer guards large plant (7)
I believe the answer is:
bloomer
'plant' is the definition.
'bouncer guards large' is the wordplay.
'bouncer' becomes 'boomer' (boomer can refer to a male kangaroo).
'guards' means one lot of letters goes inside another.
'large' becomes 'l'.
'boomer' going around 'l' is 'BLOOMER'.
(Other definitions for bloomer that I've seen before include "made by a baker" , "Large loaf; or, a mistake" , "Stupid mistake" , "Big mistake" , "Crusty loaf" .)