Top gymnast on track to win cup (5)
I believe the answer is:
grail
'win cup' is the definition.
'grail' can be an answer for 'cup' (grail is a kind of cup). I am not certain of the 'win' bit.
'top gymnast on track' is the wordplay.
'top' suggests taking the first letters (in a down clue, the first letter is top).
'on' means one lot of letters go next to another.
'track' becomes 'rail' (synonyms).
The first letter of 'gymnast' is 'g'.
'g'+'rail'='GRAIL'
'to' acts as a link.
Can you help me to learn more?
(Other definitions for grail that I've seen before include "Object of knightly quest" , "what some look for" , "The holy chalice used by Christ at the Last Supper" , "Famous chalice" , "Holy vessel used at the Last Supper" .)