Hill walker in fog could, say, wrongly (8)
I believe the answer is:
misspeak
'say wrongly' is the definition.
'hill walker in fog' is the wordplay.
I cannot really understand how this works, but
'hill' could be 'peak' and 'peak' is located in the answer.
The remaining letters 'miss' is a valid word which might be clued in a way I don't understand.
This explanation may well be incorrect...
'could' acts as a link.
(Other definitions for misspeak that I've seen before include "say, the wrong way" , "Express oneself badly" , "say, wrongly" , "Emulate Mrs Clinton" .)