Divide pair: lose fake (8)
I believe the answer is:
polarise
'divide' is the definition.
(I know that polarise is a type of divide)
'pair lose fake' is the wordplay.
'fake' indicates an anagram.
'pair'+'lose'='pairlose'
'pairlose' with letters rearranged gives 'POLARISE'.
(Other definitions for polarise that I've seen before include "divide" , "Set or become set at opposite extremes of opinion" , "Cause to adopt extreme positions - lose pair (anag)" .)