Uneven grass in Morecambe (7)
I believe the answer is:
erratic
'uneven' is the definition.
(erratic can mean uneven or unpredictable)
'grass in morecambe' is the wordplay.
'grass' becomes 'rat' (both can mean a snitch or informer).
'in' indicates putting letters inside.
'morecambe' becomes 'eric' (comedian Eric Morecambe).
'rat' put within 'eric' is 'ERRATIC'.
(Other definitions for erratic that I've seen before include "Fickle" , "Sporadic" , "on irregular path" , "Wandering" , "Changeable" .)