Beat up in barbershop, metaphorically (5)
I believe the answer is:
tempo
'beat' is the definition.
(thesaurus)
'up in barbershop metaphorically' is the wordplay.
'up' says the letters should be written in reverse (in down clue: letters go upwards).
'in' indicates a hidden word.
'opmet' is hidden in the letters of 'barbershop metaphorically'.
'opmet' backwards is 'TEMPO'.
(Other definitions for tempo that I've seen before include "Musical beat or rhythm" , "Muscial time" , "Rhythm of piece of music" , "Time (music)" , "Cadence" .)