Baddy leading soldiers in military unit (5)
I believe the answer is:
cadre
'military unit' is the definition.
(I've seen this before)
'baddy leading soldiers' is the wordplay.
'baddy' becomes 'cad' (a cad is a dishonourable person).
'leading' says to put letters next to each other (some letters go in front of others).
'soldiers' becomes 're' (Royal Engineers).
'cad'+'re'='CADRE'
'in' is the link.
(Other definitions for cadre that I've seen before include "Core group -- cared (anag)" , "Group of key personnel" , "Political group" , "Fighting unit" , "Nucleus, framework" .)