Possibly fired - a space needing to be filled (5)
I believe the answer is:
blank
'to be filled' is the definition.
Both the definition and answer are adjectives. Maybe there's a link between them I don't understand?
'possibly fired a space' is the wordplay.
I cannot really see how this works, but
'a' could be 'an' and 'an' is present in the answer.
This may be the basis of the clue (or it may be nonsense).
'needing' is the link.
Can you help me to learn more?
(Other definitions for blank that I've seen before include "Bare; not marked" , "Not written on; (look) uncomprehending" , "Bare; not decorated" , "Expressionless" , "Not written upon" .)