Mum, visibly embarrassed? A bit (5)
I believe the answer is:
shred
'a bit' is the definition.
(I've seen this before)
'mum visibly embarrassed?' is the wordplay.
'mum' becomes 'sh' (I've seen this in other clues).
'visibly embarrassed?' becomes 'red'.
'sh'+'red'='SHRED'
(Other definitions for shred that I've seen before include "Cut into small pieces" , "Small piece torn from something" , "Thin scrap or strip" , "Rip up" , "just a touch" .)