Uncertain to order dinner if tie not right (10)
I believe the answer is:
indefinite
'uncertain' is the definition.
('indefinite' can be a synonym of 'uncertain')
'order dinner if tie not right' is the wordplay.
'order' indicates an anagram.
'not' is a deletion indicator.
'right' becomes 'r' (common abbreviation).
'dinner'+'if'+'tie'='dinneriftie'
'dinneriftie' with 'r' removed is 'dinneiftie'.
'dinneiftie' anagrammed gives 'INDEFINITE'.
'to' acts as a link.
(Other definitions for indefinite that I've seen before include "Like a" , "Not certain" , "rough" , "Unsettled" , "Loose" .)