Very old, I would become unoccupied (4)
I believe the answer is:
void
'unoccupied' is the definition.
(I've seen this in another clue)
'very old i would' is the wordplay.
'very' becomes 'v' (abbreviation).
'old' becomes 'o' (common abbreviation eg in OE for Old English).
'i would' becomes 'I'd'.
'v'+'o'+'id'='VOID'
'become' acts as a link.
(Other definitions for void that I've seen before include "Not valid or legally binding" , "Gap, absence" , "Vacant; not valid" , "Blank, invalid" , "Not valid, empty space" .)