Tight-fisted international body going ahead with firing 50% makes no sense (9)

'makes no sense' is the definition.
(meaning nothing)

'tight-fisted international body going ahead with firing 50' is the wordplay.
'tight-fisted' becomes 'mean' (both can mean miserly).
'international body' becomes 'UN' (short for United Nations).
'going ahead' means one lot of letters go next to another (some letters go in front of others).
'with' means one lot of letters go next to another.
'50' suggests halving the letters.
'firing' cut in half is 'ing'.
'mean' put after 'un' is 'unmean'.
'unmean'+'ing'='UNMEANING'