Lacking skill - true aim has gone astray (10)
I believe the answer is:
amateurish
'lacking skill true aim has gone astray' is the definition.
I can't judge whether this definition defines the answer.
'true aim has gone astray' is the wordplay.
'gone astray' indicates anagramming the letters (I've seen this in other clues).
'true'+'aim'+'has'='trueaimhas'
'trueaimhas' anagrammed gives 'AMATEURISH'.
Can you help me to learn more?
(Other definitions for amateurish that I've seen before include "using little craft, perhaps" , "Lay" , "Not very professional" , "done imperfectly" , "Inept, unskilful" .)