Astonished bridge player interrupts a brawl (9)
I believe the answer is:
awestruck
'astonished' is the definition.
(I've seen this before)
'bridge player interrupts a brawl' is the wordplay.
'bridge player' becomes 'west' (name given to one player in the card game bridge).
'interrupts' means one lot of letters goes inside another.
'brawl' becomes 'ruck'.
'a'+'ruck'='aruck'
'west' put within 'aruck' is 'AWESTRUCK'.
(Other definitions for awestruck that I've seen before include "Filled with wonder" , "Stunned" , "Terrified" , "Fearful" , "Suck water (anag) - completely astonished" .)