Slugs found in mammoth (4)
I believe the answer is:
ammo
'slugs' is the definition.
(I've seen this before)
'in mammoth' is the wordplay.
'in' indicates the answer is hidden within the clue.
'AMMO' can be found hidden inside 'mammoth'.
'found' is the link.
(Other definitions for ammo that I've seen before include "Contents of magazine" , "that goes in magazine: ...?" , "eg Bullets, shells" , "Bullets, say, in short" , "round" .)