He composed line in exam papers the wrong way (7)
I believe the answer is:
vivaldi
'he composed' is the definition.
(composer Antonio Vivaldi)
'line in exam papers the wrong way' is the wordplay.
'line' becomes 'l'.
'in' means one lot of letters goes inside another.
'exam' becomes 'viva' (short for 'viva voce', an oral examination).
'papers' becomes 'ID' (identification papers).
'the wrong way' is a reversal indicator.
'id' reversed gives 'di'.
'viva'+'di'='vivadi'
'l' inserted within 'vivadi' is 'VIVALDI'.
(Other definitions for vivaldi that I've seen before include "Italian composer, Antonio (d. 1741)" , "Baroque Venetian composer, d.1741" , "Italian composer (the Red Priest) , d.1741" , "Venetian composer ("The Red Priest"), d. 1741" , "Italian composer of 'The Four Seasons'" .)