Cover up aim to embrace quiet libertine lacking energy (8)
I believe the answer is:
enshroud
'cover up' is the definition.
(thesaurus)
'aim to embrace quiet libertine lacking energy' is the wordplay.
'aim' becomes 'end' (both can mean a goal or purpose).
'to embrace' indicates putting letters inside.
'quiet' becomes 'sh' ('sh' is used to tell someone to be quiet).
'libertine lacking energy' becomes 'rou' (I can't explain this - if you can you should give a lot more credence to this answer).
'sh'+'rou'='shrou'
'end' placed around 'shrou' is 'ENSHROUD'.
Can you help me to learn more?
(Other definitions for enshroud that I've seen before include "Envelop and hide from view" , "Hide - cloak" , "Cover with a garment (or mist?)" , "Completely envelop" .)