Insect I wager is crawling (6)
I believe the answer is:
earwig
'insect' is the definition.
(I know that earwig is a type of insect)
'i wager is crawling' is the wordplay.
'is crawling' indicates an anagram (letters crawl around).
'i'+'wager'='iwager'
'iwager' anagrammed gives 'EARWIG'.
(Other definitions for earwig that I've seen before include "little insect" , "flatterer" , "Fork-tailed insect" , "A bug for Americans" , "Go in for eavesdropping" .)