With a flourish, shows a selection of fibre-rich food offerings (10)
I believe the answer is:
brandishes
'fibre-rich food offerings' is the definition.
I can't tell whether this defines the answer.
'with a flourish shows a selection' is the wordplay.
'with' means one lot of letters go next to another.
'a flourish' becomes 'brandish' (brandish is a kind of flourish).
'shows a selection' becomes 'es' (I can't justify this - if you can you should give a lot more credence to this answer).
'brandish' put next to 'es' is 'BRANDISHES'.
'of' acts as a link.
Can you help me to learn more?
(Other definitions for brandishes that I've seen before include "Flourishes" , "Shakes" .)