Army office, half lost in cyclone, rebuilt (9)

'army office' is the definition.
(office or responsibilities of a colonel)

'half lost in cyclone rebuilt' is the wordplay.
'half' suggests halving the letters.
'in' indicates putting letters inside.
'rebuilt' indicates anagramming the letters.
'lost' cut in half is 'lo'.
'cyclone' anagrammed gives 'conelcy'.
'lo' put into 'conelcy' is 'COLONELCY'.