To a saint, the pious conclusion is the flowery part! (6)
I believe the answer is:
stamen
'the flowery part' is the definition.
'stamen' can be an answer for 'part' (I have seen 'Part of flower' mean 'stamen' so perhaps 'part' could also mean 'stamen'). I'm not sure about the 'the flowery' bit.
'to a saint the pious conclusion' is the wordplay.
'to a saint' becomes 'st' (abbreviation).
'the pious conclusion' becomes 'amen' (I have seen 'Conclusion of prayer' mean 'amen' so perhaps 'conclusion' could also mean 'amen'. I am not sure about the 'pious' bit.).
'st'+'amen'='STAMEN'
'is' acts as a link.
Can you help me to learn more?
(Other definitions for stamen that I've seen before include "Male ditto" , "Pollen-bearing organ of flower" , "The pollen-bearing organ of flowering plants" , "Fertiliser" , "Flower pollen carrier" .)