Bishop at meadow with church cleaner (6)
I believe the answer is:
bleach
'cleaner' is the definition.
(I've seen this before)
'bishop at meadow with church' is the wordplay.
'bishop' becomes 'B' (abbreviation used in chess).
'at' means one lot of letters go next to another.
'meadow' becomes 'lea' (I've seen this before).
'with' means one lot of letters go next to another.
'church' becomes 'ch' (common abbreviation).
'b'+'lea'+'ch'='BLEACH'
(Other definitions for bleach that I've seen before include "Sterilising whitener" , "Whitening agent" , "Remove colour from" , "Chemically whiten" , "Blanching agent" .)