White bishop completely supporting opening from queen, we hear? (3,4)
I believe the answer is:
cue ball
'white' is the definition.
(the cue ball in snooker is also called the white)
'bishop completely supporting opening from queen we hear?' is the wordplay.
'bishop' becomes 'B' (chess abbreviation).
'completely' becomes 'all' (synonyms).
'supporting' means one lot of letters go next to another (in a down clue, some letters go below others).
'opening from' says to take the initial letters.
'we hear?' indicates a 'sounds like' (homophone) clue.
The first letter of 'queen' is 'q'.
'q' sounds like 'cue'.
'b'+'all'='ball'
'ball' put after 'cue' is 'CUE-BALL'.
(Other definitions for cue ball that I've seen before include "Object struck by a snooker player" , "The white in snooker" , "Feature of pub entertainment" , "Jimmy White's white?" .)