Mechanical tool tangles up when broken (6,3)
I believe the answer is:
staple gun
'mechanical tool' is the definition.
(tool for stapling things)
'tangles up when broken' is the wordplay.
'when broken' indicates anagramming the letters (I've seen this in other clues).
'tangles'+'up'='tanglesup'
'tanglesup' with letters rearranged gives 'STAPLE GUN'.
(Other definitions for staple gun that I've seen before include "One that fires those fixing" , "Tool for inserting fasteners" .)