Loosened up initially with new energy from performance-enhancing drug (8)
I believe the answer is:
unzipped
'loosened' is the definition.
(I've seen this before)
'up initially with new energy from performance-enhancing drug' is the wordplay.
I cannot quite see how this works, but
'new' could be 'n' (abbreviation as in New Testament NT) and 'n' is located in the answer.
'energy' could be 'zip' (I've seen this in another clue) and 'zip' is found within the answer.
'up' is within the answer.
'drug' could be 'e' (E is another name for ecstasy) and 'e' is found in the answer.
A single letter 'd' remains which might be clued in a way I don't see.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for unzipped that I've seen before include "Loosened" , "Undone (of trousers)" , "Unfastened" .)