Dispatched to cover cold trail (5)
I believe the answer is:
scent
'trail' is the definition.
(an animal's trail is its scent)
'dispatched to cover cold' is the wordplay.
'dispatched' becomes 'sent' (I've seen this in another clue).
'to cover' means one lot of letters goes inside another.
'cold' becomes 'c' (eg on taps).
'sent' placed around 'c' is 'SCENT'.
(Other definitions for scent that I've seen before include "Track; aroma" , "Whiff" , "Number of clues" , "Clue" , "Pleasant odour" .)