It's mean to keep a girl in such a long time (7)
I believe the answer is:
average
'it's mean' is the definition.
(synonyms)
'girl in such a long time' is the wordplay.
'girl' becomes 'vera' ().
'in' indicates putting letters inside.
'such a long time' becomes 'age' (an age is a period of time).
'vera' put inside 'age' is 'AVERAGE'.
'to keep a' acts as a link.
This may not be right. Some or all of it may be part of another bit of the clue.
Can you help me to learn more?
(Other definitions for average that I've seen before include "Mean, so-so" , "Middle value, the norm" , "Mean, median or middling" , "Usual - mediocre - mean" , "Mean - everyday" .)