It's autographed by engineers having quit (8)
I believe the answer is:
resigned
'quit' is the definition.
(I've seen this in another clue)
'it's autographed by engineers' is the wordplay.
'it's autographed' becomes 'signed' (similar in meaning).
'by' says to put letters next to each other.
'engineers' becomes 're' (Royal Engineers).
'signed' after 're' is 'RESIGNED'.
'having' is the link.
(Other definitions for resigned that I've seen before include "Gave up (job) voluntarily" , "Handed in one's notice to leave" , "Gave up (a post)" , "Left post" , "without hope of change" .)