Teacher, see, with popular cut of beef (7)
I believe the answer is:
sirloin
'cut of beef' is the definition.
(I've seen this before)
'teacher see with popular' is the wordplay.
'teacher' becomes 'sir' (way of addressing a male teacher).
'see' becomes 'lo' (archaic word meaning 'look!').
'with' is a charade indicator (letters next to each other).
'popular' becomes 'in'.
'sir'+'lo'+'in'='SIRLOIN'
(Other definitions for sirloin that I've seen before include "Choice cut of beef" , "Good cut of beef" , "Type of steak" , "Upper part of loin of beef" , "Quality cut of beef loin" .)