Retrieve wild deer to upset me (6)
I believe the answer is:
redeem
'retrieve' is the definition.
(I've seen this before)
'wild deer to upset me' is the wordplay.
'wild' indicates anagramming the letters.
'to upset' says the letters should be written in reverse.
'me' reversed gives 'em'.
'deer' with letters rearranged gives 'rede'.
'rede'+'em'='REDEEM'
(Other definitions for redeem that I've seen before include "Save from sin or error" , "Cash in shares, bonds etc" , "Save from sins or buy back" , "Make good" , "Get back" .)