Mouselike (6)
I believe the answer is:
rodent
'mouselike' is the definition.
(thesaurus)
This is all the clue.
(Other definitions for rodent that I've seen before include "Placental mammal having a single pair of incisor, 'gnawing', teeth" , "Mouse or squirrel, say" , "Eg, mouse, squirrel" , "Gnawing creature" , "Creature such as a rat" .)