Plain endive cooked at temperature (7)
I believe the answer is:
evident
'plain' is the definition.
(synonyms)
'endive cooked at temperature' is the wordplay.
'cooked' indicates anagramming the letters (letters cooked into a new form).
'at' means one lot of letters go next to another.
'temperature' becomes 't' (abbreviation).
'endive' with letters rearranged gives 'eviden'.
'eviden'+'t'='EVIDENT'
(Other definitions for evident that I've seen before include "Indisputable" , "Obvious, may be plainly seen" , "Quite obvious, easy to see" , "Obvious, quite apparent" , "Comprehensible - manifest" .)