Adult party including wine periodically (5-2)
I believe the answer is:
grown-up
'adult' is the definition.
(I've seen this before)
'party including wine periodically' is the wordplay.
'party' 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.
'periodically' indicates alternate letters (letters must be selected 'every so often').
The alternating letters of 'wine' are '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 "Big" , "Fully developed person" , "Mature" , "Fully-developed" , "Matured" .)