It's allocated when autographed (8)
I believe the answer is:
assigned
'it's allocated' is the definition.
(I've seen this before)
'when autographed' is the wordplay.
'when' becomes 'as' (eg 'when I walked' means 'as I walked').
'autographed' becomes 'signed' (similar in meaning).
'as'+'signed'='ASSIGNED'
(Other definitions for assigned that I've seen before include "Appointed to a duty or task" , "selected" , "Allocated" , "'Allotted, ascribed (8)'" , "Allotted or delegated" .)