In the firm the hire charge he entered was unclear (10)
I believe the answer is:
incoherent
'unclear' is the definition.
(thesaurus)
'in the firm the hire charge he entered' is the wordplay.
'the firm' becomes 'co' (a firm is a company).
'the hire charge' becomes 'rent' (I can't explain this - if you can you should give a lot more credence to this answer).
'entered' means one lot of letters goes inside another.
'co'+'rent'='corent'
'corent' enclosing 'he' is 'coherent'.
'in'+'coherent'='INCOHERENT'
'was' acts as a link.
Can you help me to learn more?
(Other definitions for incoherent that I've seen before include "rambling" , "drunk?" , "Internally inconsistent" , "difficult to understand" , "Confused" .)