His suffering has no legal force (7)
I believe the answer is:
invalid
'his suffering has no legal force' is the definition.
The answer is a person as well as being a singular noun. This is suggested by the definition.
'his suffering has no legal' is the wordplay.
'his suffering' becomes 'i' (I can't explain this - if you can you should give a lot more credence to this answer).
'has' says to put letters next to each other.
'no' becomes 'n' (common abbreviation y/n).
'legal' becomes 'valid' (similar in meaning).
'i'+'n'+'valid'='INVALID'
Can you help me to learn more?
(Other definitions for invalid that I've seen before include "Legally void" , "Nugatory" , "Without legal force" , "Void; patient" , "Unsound; ill person" .)