In addition to being no less fit then (2,4,2)
I believe the answer is:
as well as
'in addition to' is the definition.
(I've seen this in another clue)
'being no less fit then' is the wordplay.
I cannot really understand how this works, but
'being' could be 'swell' (swell is a kind of being) and 'swell' is present in the answer.
The remaining letters 'aas' is a valid word which might be clued in a way I don't see.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for as well as that I've seen before include "Along with" , "In addition to (2, 4, 2)" , "In addition to, also" , "Supplementing" , "No less than" .)