The decentralised forces of the enemies (4)
I believe the answer is:
foes
'the enemies' is the definition.
(I've seen this before)
'the decentralised forces' is the wordplay.
'the decentralised' means to remove the middle letters (the centre of the word is removed).
'forces' with its middle taken out is 'FOES'.
'of' acts as a link.
(Other definitions for foes that I've seen before include "Enemies" , "Adversaries" .)