Plain girl set up to enter item in sports programme (7)
I believe the answer is:
evident
'plain' is the definition.
(synonyms)
'girl set up to enter item in sports programme' is the wordplay.
'girl' becomes 'di'.
'set up' shows that the letters should be reversed in order.
'to enter' indicates putting letters inside.
'item in sports programme' becomes 'event' (I've seen this before).
'di' written backwards gives 'id'.
'id' placed inside 'event' is 'EVIDENT'.
(Other definitions for evident that I've seen before include "Easy to understand" , "Plain to see" , "Quite obvious and clear" , "'Plain, apparent (7)'" , "Conspicuous" .)