Fellows upset over nothing worked alone (4,4)
I believe the answer is:
flew solo
'worked alone' is the definition.
I know nothing about this answer so I cannot judge whether it can be defined by this definition.
'fellows upset over nothing' is the wordplay.
'upset' indicates an anagram.
'over' indicates putting letters inside.
'nothing' becomes 'O' (O resembles 0).
'fellows' with letters rearranged gives 'flewslo'.
'flewslo' placed around 'o' is 'FLEW SOLO'.
Can you help me to learn more?
(Another definition for flew solo that I've seen is " So fellow took to the air alone?".)