Would it not be an open and shut case without him? (3,7)

'would it not be an open and shut case without him?' is the definition.
The definition suggests a singular noun which matches the answer.

'it not be an open and shut case without him?' is the wordplay.
I cannot quite see how this works, but
'it' could be 't' (abbreviation. e.g. in 'tis) and 't' is found in the answer.
'an' could be 'i' (Roman numeral for one) and 'i' is located in the answer.
'and' could be 'n' (common abbreviation for 'and') and 'n' is found in the answer.
'him?' could be 'wes' and 'wes' is found in the remaining letters.
The remaining letters 'keys' is a valid word which might be clued in a way I don't see.
This may be the basis of the clue (or it may be nonsense).

Can you help me to learn more?