One inexperienced guy with no rest at work (9)
I believe the answer is:
youngster
'one inexperienced' is the definition.
I can't tell whether this definition defines the answer.
'guy with no rest at work' is the wordplay.
'with' means one lot of letters go next to another.
'at work' indicates an anagram.
'no'+'rest'='norest'
'guy' after 'norest' is 'norestguy'.
'norestguy' is an anagram of 'YOUNGSTER'.
Can you help me to learn more?
(Other definitions for youngster that I've seen before include "Person of tender years" , "tyke" , "Kid" , "one of tender years" , "Stripling" .)