Supervise lines in Old English (7)
I believe the answer is:
oversee
'supervise' is the definition.
(synonyms)
'lines in old english' is the wordplay.
'lines' becomes 'verse' (I've seen this before).
'in' indicates putting letters inside.
'old english' becomes 'oe'.
'verse' inserted inside 'oe' is 'OVERSEE'.
(Other definitions for oversee that I've seen before include "What superintendent will do" , "Inspect" , "As supervisor does" , "Supervise, keep an eye on" , "Disregard" .)