Rescue fierce creature, grabbing end of tail (7)
I believe the answer is:
salvage
'rescue' is the definition.
(I know that salvage is a more specific form of the action rescue)
'fierce creature grabbing end of tail' is the wordplay.
'fierce creature' becomes 'savage' (savage can mean a fierce beast).
'grabbing' indicates putting letters inside.
'end of' suggests the final letters.
The final letter of 'tail' is 'l'.
'savage' enclosing 'l' is 'SALVAGE'.
(Other definitions for salvage that I've seen before include "Preserve" , "Rescue of property from peril" , "Rescued sunken cargo" , "Reclaim" , "Save - junk" .)