Greek goddess banning husband for long time (3)
I believe the answer is:
era
'long time' is the definition.
(a long period of time)
'greek goddess banning husband' is the wordplay.
'greek goddess' becomes 'hera' (I've seen this before).
'banning' indicates named letters should be taken away.
'husband' becomes 'h'.
'hera' with 'h' removed is 'ERA'.
'for' acts as a link.
(Other definitions for era that I've seen before include "Long historic period" , "Long stretch" , "Distinctive period of time" , "Age marked by a distinctive character" , "Distinct period in history" .)