Development happens here when ship enters dead space (4,4)

'development happens here' is the definition.
(film is developed in a dark room)

'ship enters dead space' is the wordplay.
'ship' becomes 'ark' (as in Noah's ark).
'enters' means one lot of letters goes inside another.
'dead' becomes 'd' (abbreviation in government records).
'space' becomes 'room' (enough space or room to do something).
'd'+'room'='droom'
'ark' put inside 'droom' is 'DARK-ROOM'.

'when' is the link.