A tiller turned out to be exact (7)
I believe the answer is:
literal
'to be exact' is the definition.
('literal' can be similar in meaning to 'exact')
'a tiller turned' is the wordplay.
'turned' is an anagram indicator.
'a'+'tiller'='atiller'
'atiller' with letters rearranged gives 'LITERAL'.
'out' is the link.
(Other definitions for literal that I've seen before include "All tire (anag.)" , "Tell IRA (anag) - word for word" , "Textual error" , "primary sense" , "Word-for-word" .)