Baby group starts with some trigonometry (6)
I believe the answer is:
cosset
'baby' is the definition.
(synonyms)
'group starts with some trigonometry' is the wordplay.
I cannot really understand how this works, but
'group' could be 'set' (both can mean a collection) and 'set' is present in the answer.
The remaining letters 'cos' 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 cosset that I've seen before include "Protect overindulgently" , "Care for overindulgently" , "pet" , "Pamper, mollycoddle" , "Pamper and spoil" .)