Officers ordering a ride aboard sailing ships (10)

'officers' is the definition.
(brigadier is a kind of officer)

'ordering a ride aboard sailing ships' is the wordplay.
'ordering' indicates anagramming the letters.
'aboard' is an insertion indicator.
'sailing ships' becomes 'brigs' (brig is a kind of sailing ship).
'a'+'ride'='aride'
'aride' with letters rearranged gives 'adier'.
'adier' inserted inside 'brigs' is 'BRIGADIERS'.