It's not often there are new models (6)
I believe the answer is:
seldom
'it's not often' is the definition.
('seldom' is the opposite to 'often')
'new models' is the wordplay.
'new' indicates an anagram.
'models' anagrammed gives 'SELDOM'.
'there are' is the link.
This may not be correct. Some or all of it may be part of another bit of the clue.
Can you help me to learn more?
(Other definitions for seldom that I've seen before include "Alluvium" , "Not very often, rarely" , "Not often, infrequently" , "Not 21" , "Only occasionally" .)