Iris gets no return on large bottle (6)
I believe the answer is:
flagon
'large bottle' is the definition.
(I've seen this before)
'iris gets no return' is the wordplay.
'iris' becomes 'flag' (synonyms).
'gets' is a charade indicator (letters next to each other).
'return' shows that the letters should be reversed in order.
'no' in reverse letter order is 'on'.
'flag'+'on'='FLAGON'
'on' acts as a link.
(Other definitions for flagon that I've seen before include "Large vessel with a handle and spout" , "Large drinks container" , "Wine jug" , "Large rounded bottle for cider or wine" , "Drinking vessel" .)