Porterhouse perhaps admitting right run of luck? (6)
I believe the answer is:
streak
'run of luck?' is the definition.
(I've seen this before)
'porterhouse perhaps admitting right' is the wordplay.
'porterhouse perhaps' becomes 'steak' (porterhouse is a kind of steak).
'admitting' means one lot of letters goes inside another.
'right' becomes 'r' (common abbreviation).
'steak' enclosing 'r' is 'STREAK'.
(Other definitions for streak that I've seen before include "Skater (anag.)" , "feature of bacon" , "irregular line of colour" , "run? Barely!" , "Dash (in the nude?)" .)