Gents maybe assuming bike races to be a children’s game? (5)
I believe the answer is:
lotto
'a children's game?' is the definition.
(children's game similar to bingo)
'gents maybe assuming bike races' is the wordplay.
I cannot really see how this works, but
'races' could be 'tt' (Isle of Man Tourist Trophy races) and 'tt' is present in the answer.
'gents' could be 'loo' (I've seen this in other clues) and 'loo' is found within the remaining letters.
No letters remain.
This explanation may well be incorrect...
'to be' is the link.
Can you help me to learn more?
(Other definitions for lotto that I've seen before include "Bingo-like game" , "Game of chance involving balls" , "Game like bingo" , "form of gambling" , "chancy business" .)