Brief opportunity to secure Omani, perhaps, as coach (9)
I believe the answer is:
charabanc
'coach' is the definition.
(type of coach or bus)
'brief opportunity to secure omani perhaps' is the wordplay.
'brief' means to remove the last letter.
'opportunity' becomes 'chance' (synonyms).
'to secure' is an insertion indicator.
'omani perhaps' becomes 'arab' (an Omani is a person from Oman).
'chance' with its last letter taken off is 'chanc'.
'chanc' placed around 'arab' is 'CHARABANC'.
'as' acts as a link.
(Other definitions for charabanc that I've seen before include "Old tourist coach" , "E.g. transport" , "Old vehicle" , "Former coach" , "Early coach" .)