Bishop uses a smaller amount to anoint them (5)
I believe the answer is:
bless
'amount to anoint them' is the definition.
I can't tell whether this definition defines the answer.
'bishop uses a smaller' is the wordplay.
I cannot quite see how this works, but
'bishop' could be 'b' (abbreviation for bishop in chess) and 'b' is present in the answer.
'smaller' could be 'less' (less great in size) and 'less' is found in the answer.
No letters remain.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for bless that I've seen before include "Give benediction" , "Endow; praise" , "Make holy" , "Pray for" , "Order of service" .)