Amusing nobleman turning left (5)
I believe the answer is:
droll
'amusing' is the definition.
(I've seen this before)
'nobleman turning left' is the wordplay.
'nobleman' becomes 'lord' (synonyms).
'turning' says the letters should be written in reverse.
'left' becomes 'l' (common abbreviation).
'lord' reversed gives 'drol'.
'drol'+'l'='DROLL'
(Other definitions for droll that I've seen before include "Quaintly amusing" , "Funny" , "Comic" , "Mildly amusing" , "amusing, in a strange way" .)