Smallest, not large bearing (4)
I believe the answer is:
east
'bearing' is the definition.
(a compass bearing)
'smallest not large' is the wordplay.
'smallest' becomes 'least' (synonyms).
'not' indicates named letters should be taken away.
'large' becomes 'L' (eg in clothes sizes).
'least' with 'l' taken away is 'EAST'.
(Other definitions for east that I've seen before include "Player in deal" , "course" , "Compass bearing" , "Cardinal compass point" , "On most maps it's right!" .)