Caution - dubious gift horse! (9)
I believe the answer is:
foresight
'caution' is the definition.
(I've seen this before)
'dubious gift horse' is the wordplay.
'dubious' indicates an anagram.
'gift'+'horse'='gifthorse'
'gifthorse' with letters rearranged gives 'FORESIGHT'.
(Other definitions for foresight that I've seen before include "Ability to anticipate" , "Prudence" , "Anticipation" , "Clairvoyance" , "Vision" .)