Mate grabbing short chef's big knife (7)
I believe the answer is:
machete
'big knife' is the definition.
'machete' can be an answer for 'knife' (I've seen this before). I'm not certain of the 'big' bit.
'mate grabbing short chef's' is the wordplay.
'grabbing' is an insertion indicator.
'short' means to remove the last letter.
'chef' with its last letter removed is 'che'.
'mate' going around 'che' is 'MACHETE'.
Can you help me to learn more?
(Other definitions for machete that I've seen before include "cutter" , "Jungle blade" , "Knife for hacking" , "Broad heavy knife used in S America" , "A heavy-duty jungle knife" .)