Witty nobleman sent up line (5)
I believe the answer is:
droll
'witty' is the definition.
(I've seen this in another clue)
'nobleman sent up line' is the wordplay.
'nobleman' becomes 'lord' (synonyms).
'sent up' is a reversal indicator.
'line' becomes 'l' (used when specifying particular lines from a poem).
'lord' in reverse letter order is 'drol'.
'drol'+'l'='DROLL'
(Other definitions for droll that I've seen before include "Funny" , "Amusing - jester" , "Mildly amusing" , "Drily amusing" , "Humorous or whimsical" .)