Magnificent nose broken by nice deceptive left (8)
I believe the answer is:
princely
'magnificent' is the definition.
(fit for a prince)
'nose broken by nice deceptive left' is the wordplay.
'nose' becomes 'pry' (to nose around is to pry).
'broken by' indicates putting letters inside.
'deceptive' indicates anagramming the letters.
'left' becomes 'L' (common abbreviation).
'nice' is an anagram of 'ince'.
'ince'+'l'='incel'
'pry' going around 'incel' is 'PRINCELY'.
(Other definitions for princely that I've seen before include "Magnificent" , "Very grand, in the manner of a royal" , "In the manner of a regal son" , "Lavish (like Charles?)" , "like Hamlet?" .)