Wastrel disliked holding himself back (5)
I believe the answer is:
idler
'wastrel' is the definition.
(I've seen this before)
I can't explain the rest of the clue.
Can you help me to learn more?
(Other definitions for idler that I've seen before include "Layabout; ship crewman not on watch" , "One who loafs about" , "bad worker" , "Lazybones; gear wheel" , "Slacker" .)