Watch dance in which pupil's seen? (7)
I believe the answer is:
eyeball
'in which pupil's seen?' is the definition.
(I know that pupil is part of eyeball)
'watch dance' is the wordplay.
'watch' becomes 'eye' (eye can mean to watch or look at).
'dance' becomes 'ball' (ball is a kind of dance).
'eye'+'ball'='EYEBALL'
(Other definitions for eyeball that I've seen before include "Socket filler" , "Label ye (anag)" , "Look confrontationally" , "" - to - " = in close confrontation" , "Organ of sight" .)