Window in church shows singer of colour (9)
I believe the answer is:
chaffinch
'singer of colour' is the definition.
(I know that chaffinch is a subclass of colorful songbird)
'window in church' is the wordplay.
'window' becomes 'chaff' (both can mean an anti-missile measure).
'church' becomes 'ch' (common abbreviation).
'chaff'+'in'+'ch'='CHAFFINCH'
'shows' acts as a link.
(Other definitions for chaffinch that I've seen before include "Small European songbird" , "European bird with black and white wings" , "flier" , "Common bird" , "Singer" .)