Finally producing map book at a loss (6)
I believe the answer is:
atlast
'a loss' is the definition.
I know nothing about this answer so I can't tell whether this works.
'finally producing map book at' is the wordplay.
I cannot quite see how this works, but
'finally' could be 'last' (synonyms) and 'last' is found within the answer.
'at' is present in the answer.
No letters remain.
This explanation may well be incorrect...
Can you help me to learn more?
(Another definition for atlast that I've seen is " ultimately".)