Watch dance in which one has pupil (7)
I believe the answer is:
eyeball
'one has pupil' is the definition.
'eyeball' can be an answer for 'pupil' (thesaurus). I am not certain of the 'one has' bit.
'watch dance' is the wordplay.
'watch' becomes 'eye' (I've seen this before).
'dance' becomes 'ball' (ball is a kind of dance).
'eye'+'ball'='EYEBALL'
'in which' is the link.
Can you help me to learn more?
(Other definitions for eyeball that I've seen before include "Closely examine" , "making us stare" , "Stare at closely (colloq.)" , "It was cut in Un Chien Andalou" , "Stare at closely; organ" .)