Closed openings for young students in sports (4)
I believe the answer is:
toys
'sports' is the definition.
(I've seen this before)
'closed openings for young students' is the wordplay.
'closed' becomes 'to' (as in a door closed to).
'openings for' suggests taking the first letters (the letters which open the words).
The initial letters of 'young students' is 'ys'.
'to'+'ys'='TOYS'
'in' acts as a link.
(Other definitions for toys that I've seen before include "Fiddles" , "Plays (with something), not seriously" , "Matters of no importance" , "Chihuahuas?" , "Small dogs" .)