Mature set of people including wife and children, ultimately (5-2)
I believe the answer is:
grown-up
'mature' is the definition.
(I've seen this before)
'set of people including wife and children ultimately' is the wordplay.
'set of people' becomes 'group' (I can't justify this - if you can you should give a lot more credence to this answer).
'including' is an insertion indicator.
'wife' becomes 'w' (abbreviation).
'and' says to put letters next to each other.
'ultimately' suggests the final letters.
The final letter of 'children' is 'n'.
'w'+'n'='wn'
'group' going around 'wn' is 'GROWN-UP'.
Can you help me to learn more?
(Other definitions for grown-up that I've seen before include "Fully-developed" , "Big" , "Matured" , "Adult" , "Fully developed person" .)