Men are not properly organised in a small unit (9)
I believe the answer is:
nanometre
'a small unit' is the definition.
(I've seen this before)
'men are not properly organised' is the wordplay.
'properly organised' indicates anagramming the letters.
'men'+'are'+'not'='menarenot'
'menarenot' with letters rearranged gives 'NANOMETRE'.
'in' acts as a link.
(Other definitions for nanometre that I've seen before include "A very small length" , "small unit" , "tiny distance" , "Some tiny measure" , "short distance" .)