The offer of money may make him cross (8)
I believe the answer is:
ferryman
'the offer of money may make him cross' is the definition.
The answer is a person as well as being a singular noun. This is suggested by the definition.
'may make him cross' is the wordplay.
I cannot really understand how this works, but
an anagram of 'may' is 'yma' which is within the answer.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for ferryman that I've seen before include "Transporter across water" , "Aquatic taxi driver" , "eg Charon (on the Styx)" , "He rows people across a river, like Charon" , "One plying a short water crossing" .)