A second group offering something worth having (5)
I believe the answer is:
asset
'something worth having' is the definition.
(an asset is something valuable or useful)
'a second group' is the wordplay.
'second' becomes 's' (common abbreviation).
'group' becomes 'set' (both can mean a collection).
'a'+'s'+'set'='ASSET'
'offering' acts as a link.
(Other definitions for asset that I've seen before include "Valuable person" , "valuable sort" , "- - -stripper" , "Useful item" , "virtue" .)