Wandering bear destroyed allotment (10)
I believe the answer is:
aberration
'wandering' is the definition.
(I've seen this before)
'bear destroyed allotment' is the wordplay.
'destroyed' is an anagram indicator.
'allotment' becomes 'ration' (I've seen this in other clues).
'bear' is an anagram of 'aber'.
'aber'+'ration'='ABERRATION'
(Other definitions for aberration that I've seen before include "Deviation from the accepted norm" , "irregularity" , "Unwelcome deviation from normal" , "moral lapse" , "departure from normal" .)