Wandering rodent getting in damaged rice (7)
I believe the answer is:
erratic
'wandering' is the definition.
(synonyms)
'rodent getting in damaged rice' is the wordplay.
'rodent' becomes 'rat' (rat is a kind of rodent).
'getting in' is an insertion indicator.
'damaged' indicates anagramming the letters.
'rice' with letters rearranged gives 'eric'.
'rat' placed inside 'eric' is 'ERRATIC'.
(Other definitions for erratic that I've seen before include "Irregular or uneven in movement or habit" , "hit-and-miss" , "Liable to sudden unpredictable change" , "Irregular and unreliable" , "Unstable" .)