Tenacious aim brings disaster (6,3)
I believe the answer is:
sticky end
'disaster' is the definition.
(I've seen this before)
'tenacious aim' is the wordplay.
'tenacious' becomes 'sticky' (tenacious can mean sticky or gluey).
'aim' becomes 'end' (both can mean a goal or purpose).
'sticky'+'end'='STICKY END'
'brings' is the link.
(Other definitions for sticky end that I've seen before include "Unpleasant conclusion" , "Unpleasant death" , "disaster" , "Unhappy destiny" .)