Finally grasping conclusion of debate, if nothing else (2,5)
I believe the answer is:
at least
'if nothing else' is the definition.
(I've seen this before)
'finally grasping conclusion of debate' is the wordplay.
'finally' becomes 'atlast' ('at last' can be a synonym of 'finally').
'grasping' means one lot of letters goes inside another.
'conclusion of' says to take the final letters.
The last letter of 'debate' is 'e'.
'atlast' placed around 'e' is 'AT LEAST'.
(Other definitions for at least that I've seen before include "however" , "No less than" , "Eat salt (anag) - if nothing else" , "Anyway" , "'If nothing else (2,5)'" .)