Difficult spot in which to turn left (7)
I believe the answer is:
stroppy
'difficult' is the definition.
(I've seen this before)
'spot in which to turn left' is the wordplay.
'spot' becomes 'spy' ('spy' can be a synonym of 'spot'**).
'in which' means one lot of letters goes inside another.
'to turn' says the letters should be written in reverse.
'left' becomes 'port' (left side of a ship - opposite of starboard).
'port' backwards is 'trop'.
'spy' going around 'trop' is 'STROPPY'.
(Other definitions for stroppy that I've seen before include "like a razor-sharpener?" , "Awkward to handle" , "Ill-tempered" , "Bolshie" , "Difficult" .)