Open at an end? Head for Turnberry (5)
I believe the answer is:
overt
'open' is the definition.
(I know that open can be written as overt)
'at an end? head for turnberry' is the wordplay.
'at an end?' becomes 'over' (I've seen this in another clue).
'head for' suggests taking the first letters.
The initial letter of 'turnberry' is 't'.
'over'+'t'='OVERT'
(Other definitions for overt that I've seen before include "Open, up front" , "Not locked away" , "Explicit" , "Patent, evident" , "Open, not 1 across" .)