Someone at large promontory in opposite direction to WNW (7)
I believe the answer is:
escapee
'someone at large' is the definition.
(an escapee is free or at large)
'promontory in opposite direction to wnw' is the wordplay.
'promontory' becomes 'cape' (both can mean a headland).
'in' is an insertion indicator.
'opposite direction to wnw' becomes 'ESE' (east by southeast, not west by northwest).
'cape' going within 'ese' is 'ESCAPEE'.
(Other definitions for escapee that I've seen before include "One that's broken free" , "Jail-breaker" , "One who got away" , "Runaway" , "Absconder, fugitive" .)