His maps I’d put in a mess somewhere on board (9)
I believe the answer is:
amidships
'his maps i'd' is the definition.
The definition suggests a singular noun but the answer is not.
'put in a mess somewhere on board' is the wordplay.
'put' is an insertion indicator.
'in' becomes 'hip' (both can mean fashionable).
'a mess somewhere' becomes 'amid' (I can't explain this - if you can you should give a lot more credence to this answer).
'on board' becomes 'ss' (I've seen this in other clues).
'amid'+'ss'='amidss'
'hip' placed into 'amidss' is 'AMIDSHIPS'.
Can you help me to learn more?
(Other definitions for amidships that I've seen before include "Toward the centre of the vessel" , "core on board" , "At the centre of a boat" , "nautical location?" , "Centrally on board" .)