Former student goes over lines for counterpart (7)
I believe the answer is:
obverse
'for counterpart' is the definition.
(I've seen this in another clue)
'former student goes over lines' is the wordplay.
'former student' becomes 'OB' (abbreviation for 'Old Boy').
'goes over' means one lot of letters go next to another.
'lines' becomes 'verse' (lines of poetry).
'ob'+'verse'='OBVERSE'
(Other definitions for obverse that I've seen before include "Opposite - side of coin" , "Face of a coin" , "Verbose on the opposite side" , "Verbose about coin side" , "Side of coin that bears head or principle design" .)