Unpleasantly sticky marks in stiff sticky earth (6)
I believe the answer is:
clammy
'unpleasantly sticky' is the definition.
(I've seen this before)
'marks in stiff sticky earth' is the wordplay.
I cannot quite understand how this works, but
'marks' could be 'mm' (symbol for the former German currency repeated) and 'mm' is found in the answer.
'stiff' could be 'clay' (synonyms) and 'clay' is located in the leftover letters.
This accounts for all the letters.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for clammy that I've seen before include "(Of weather) sticky" , "Unpleasantly cool and humid" , "Dank" , "Unpleasantly sticky and moist" , "Moist and adhesive" .)