A grant secured by the gymnast, maybe (7)
I believe the answer is:
athlete
'gymnast maybe' is the definition.
(I know that gymnast is a type of athlete)
'a grant secured by the' is the wordplay.
'grant' becomes 'let' (I've seen this in another clue).
'secured by' is an insertion indicator (inserted letters are held or secured).
'let' put within 'the' is 'thlete'.
'a'+'thlete'='ATHLETE'
(Other definitions for athlete that I've seen before include "front-runner, possibly" , "One may run" , "Sport participant" , "The late one is very fit, oddly" , "expected to be agile, of course" .)