Loner we led astray to become a worthless person (4-2-4)
I believe the answer is:
neer-do-well
'a worthless person' is the definition.
(I've seen this before)
'loner we led astray' is the wordplay.
'astray' indicates anagramming the letters.
'loner'+'we'+'led'='lonerweled'
'lonerweled' anagrammed gives 'NEER-DO-WELL'.
'to become' acts as a link.
(Other definitions for neer-do-well that I've seen before include "Good-for-nothing" , "Useless person" , "Useless type" , "Wastrel" , "Lazy irresponsible person" .)