Decadent and dainty, covered in slippery sludge by conservationists (4-9)
I believe the answer is:
self-indulgent
'decadent' is the definition.
(similar in meaning)
'dainty covered in slippery sludge by conservationists' is the wordplay.
I cannot really see how this works, but
'dainty' could be 'elfin' (I've seen this before) and 'elfin' is present in the answer.
an anagram of 'sludge' is 'sdulge' which is located in the remaining letters.
'conservationists' could be 'nt' (abbreviation for National Trust) and 'nt' is found within the answer.
This accounts for all the letters.
This may be the basis of the clue (or it may be nonsense).
'and' acts as a link.
Can you help me to learn more?
(Another definition for self-indulgent that I've seen is " Hedonistic".)