Indeed a saint, working at the brewery! (5)
I believe the answer is:
yeast
'working at the brewery' is the definition.
I can't judge whether this definition defines the answer.
'indeed a saint' is the wordplay.
'indeed' becomes 'yea' (I've seen this before).
'a saint' becomes 'st' (abbreviation).
'yea'+'st'='YEAST'
Can you help me to learn more?
(Other definitions for yeast that I've seen before include "Rising agent" , "As yet (anag)" , "Fungus used to ferment sugar" , "lifting agent" , "Brewer" .)