A bit quiet and embarrassed (5)
I believe the answer is:
shred
'a bit' is the definition.
(I've seen this before)
'quiet and embarrassed' is the wordplay.
'quiet' becomes 'sh' (both can be said to tell someone to be quiet).
'and' says to put letters next to each other.
'embarrassed' becomes 'red' (someone may blush or go red when embarrassed).
'sh'+'red'='SHRED'
(Other definitions for shred that I've seen before include "Small part" , "Rip up" , "Torn-off fragment" , "Bit; cut or tear into tiny strips" , "Torn piece of material" .)