Maiden groomed longer dog (7)
I believe the answer is:
mongrel
'dog' is the definition.
(I know that mongrel is a type of dog)
'maiden groomed longer' is the wordplay.
'maiden' becomes 'm' (cricket abbreviation).
'groomed' indicates anagramming the letters (letters groomed or tidied up).
'longer' anagrammed gives 'ongrel'.
'm'+'ongrel'='MONGREL'
(Other definitions for mongrel that I've seen before include "Dog of no clear breed" , "Non-pedigree" , "bastard" , "Cur" , "mixed stock" .)