Separates and suddenly shows an interest, holding power line (6,2)
I believe the answer is:
splits up
'separates' is the definition.
('split up' can be a synonym of 'separate')
'suddenly shows an interest holding power line' is the wordplay.
'suddenly shows an interest' becomes 'sits up' (sits up and listens).
'holding' indicates putting letters inside.
'power' becomes 'p' (symbol in physics).
'line' becomes 'l' (used when specifying particular lines from a poem).
'p'+'l'='pl'
'sitsup' going around 'pl' is 'SPLITS UP'.
'and' acts as a link.
(Another definition for splits up that I've seen is " Pulls apart".)