It's obvious I'd enter the contest (7)
I believe the answer is:
evident
'it's obvious' is the definition.
(similar in meaning)
'i'd enter the contest' is the wordplay.
'enter' means one lot of letters goes inside another.
'the contest' becomes 'event' (event can mean a sporting competition).
'id' inserted within 'event' is 'EVIDENT'.
(Other definitions for evident that I've seen before include "Comprehensible - manifest" , "Obvious, may be plainly seen" , "Clear to see" , "Patent" , "Quite obvious, manifest" .)