Dismayed to have had winning position after opening (8)
I believe the answer is:
startled
'dismayed' is the definition.
(thesaurus)
'had winning position after opening' is the wordplay.
I cannot quite see how this works, but
'had' could be 'led' (leading is a kind of having) and 'led' is present in the answer.
'opening' could be 'start' (both can mean the beginning) and 'start' is found in the answer.
This accounts for all the letters.
This may be the basis of the clue (or it may be nonsense).
'to have' is the link.
Can you help me to learn more?
(Other definitions for startled that I've seen before include "Stunned, shocked" , "Frightened or suprised suddenly" , "Shocked, alarmed" , "Taken aback" , "Caused sudden alarm" .)