Adult, extremely short, mature and mean? (7)
I believe the answer is:
average
'mean?' is the definition.
(mean is a kind of average)
'adult extremely short mature' is the wordplay.
'adult' becomes 'a' (abbreviation).
'extremely short' becomes 'ver' (I've seen this in other clues).
'mature' becomes 'age' (synonyms).
'a'+'ver'+'age'='AVERAGE'
'and' is the link.
(Other definitions for average that I've seen before include "Usual - mediocre - mean" , "Medial" , "mean maybe" , "It may be mean" , "Normal amount" .)