Old American prison allowing inmates to come and go (4)
I believe the answer is:
open
'go' is the definition.
(opening is a kind of going)
'old american prison' is the wordplay.
'old' becomes 'o' (common abbreviation eg in OE for Old English).
'american prison' becomes 'pen' (short for penitentiary).
'o'+'pen'='OPEN'
'allowing inmates to come and' is the link.
I am not very happy about this link. Some or all of it may belong to another bit of the clue.
Can you help me to learn more?
(Other definitions for open that I've seen before include "This championship includes both professional and amateur golfers" , "Frank - ready for business" , "Plain" , "Frank - unsettled" , "still in debate" .)