Line from 'Lepanto' (Chesterton) (4)
I believe the answer is:
oche
'line' is the definition.
(I've seen this before)
'from lepanto chesterton' is the wordplay.
'from' indicates a hidden word.
'OCHE' is hidden within 'lepanto chesterton'.
(Other definitions for oche that I've seen before include "Line from which dart-player throws" , "Line where dart thrower stands" , "Dart player's mark" , "Line at which darts player stands to throw" , "sporting line" .)