Horse I see, and a nearly dead man astride it? (7)

'horse i see' is the definition.
The definition suggests a singular noun which matches the answer.

'a nearly dead man astride it?' is the wordplay.
I cannot quite understand how this works, but
'a' is found in the answer.
'dead' could be 'd' (abbreviation in government records) and 'd' is present in the answer.
'man' could be 'bo' and 'bo' is found within the answer.
The remaining letters 'ich' is a valid word which might be clued in a way I don't understand.
This explanation may well be incorrect...

'and' is the link.

Can you help me to learn more?