Study classics, bar first quarter, collecting cup (12)
I believe the answer is:
astrophysics
'study' is the definition.
(astrophysics is a kind of study)
'bar first quarter collecting cup' is the wordplay.
'bar first' becomes 'assic' (I am not sure about this - if you are sure you should believe this answer much more).
'quarter' becomes 's'.
'collecting' indicates putting letters inside.
'cup' becomes 'trophy' (I've seen this before).
'assic'+'s'='assics'
'assics' going around 'trophy' is 'ASTROPHYSICS'.
'classics' is the link.
This may not be right. It may be part of another bit of the clue.
(Other definitions for astrophysics that I've seen before include "Branch of science" , "Science of the properties of celestial bodies" , "Science of stars and galaxies" .)