Gather port swallowed is less good (8)
I believe the answer is:
inferior
'less good' is the definition.
(I've seen this before)
'gather port swallowed' is the wordplay.
'gather' becomes 'infer' (synonyms).
'port' becomes 'rio' (Rio de Janeiro is a port).
'swallowed' is an insertion indicator.
'infer' going around 'rio' is 'INFERIOR'.
'is' is the link.
(Other definitions for inferior that I've seen before include "Less important, valuable" , "Subordinate" , "not vintage" , "badly done?" , "Second-class" .)