Chance to have managed government department being set up (6)
I believe the answer is:
random
'chance' is the definition.
(similar in meaning)
'managed government department being set up' is the wordplay.
'managed' becomes 'ran' (both can mean organised or was in charge of).
'government department' becomes 'mod' (Ministry of Defence).
'being set up' is a reversal indicator (in a down clue, letters go up).
'mod' in reverse letter order is 'dom'.
'ran'+'dom'='RANDOM'
'to have' is the link.
(Other definitions for random that I've seen before include "Sporadic" , "Occurring by chance, no fixed pattern" , "unmethodical" , "Wild" , "Haphazard, with no particular plan" .)