Blow it! I may be stuck behind this big creature (6)
I believe the answer is:
wapiti
'big creature' is the definition.
(type of deer)
'blow it i may be stuck behind this' is the wordplay.
'blow' becomes 'wap' (historical dialect term meaning a hit or thump).
'may be stuck behind this' says to put letters next to each other.
'wap'+'it'+'i'='WAPITI'
(Other definitions for wapiti that I've seen before include "I paw it (anag) - large North American deer" , "Large N. Am. red deer" , "North American native" , "Animal" , "Red deer - I paw it (anag)" .)