Government ministry united by overdue change (8)
I believe the answer is:
modulate
'change' is the definition.
(thesaurus)
'government ministry united by overdue' is the wordplay.
'government ministry' becomes 'mod' (abbreviation for Ministry of Defence).
'united' becomes 'u'.
'by' is a charade indicator (letters next to each other).
'overdue' becomes 'late' ('late' can be similar in meaning to 'overdue').
'mod'+'u'+'late'='MODULATE'
(Other definitions for modulate that I've seen before include "Adjust tone or pitch" , "Attune" , "Adjust, soften" , "Vary the tone or pitch of one's voice" , "Regulate" .)