Mat crisis involved weapons (9)
I believe the answer is:
scimitars
'weapons' is the definition.
(scimitar is a kind of weapon)
'mat crisis involved' is the wordplay.
'involved' is an anagram indicator (involved can mean confusing or complex).
'mat'+'crisis'='matcrisis'
'matcrisis' is an anagram of 'SCIMITARS'.
(Other definitions for scimitars that I've seen before include "Weapons" , "Turkish swords" .)