Work in the theatre, or just over half of one (5)
I believe the answer is:
opera
'work in the theatre' is the definition.
'opera' can be an answer for 'theatre' (opera is a kind of theatre). I am unsure of the 'work in the' bit.
'just over half of one' is the wordplay.
'just' becomes 'op' (I am not sure about this - if you are sure you should believe this answer much more).
'half of' suggests halving the letters.
'one' becomes 'a' (a thing is one thing).
'over' cut in half is 'er'.
'op'+'er'+'a'='OPERA'
'or' is the link.
Can you help me to learn more?
(Other definitions for opera that I've seen before include "Lulu, say" , "Throw a rope for the musical" , "musical presentation" , "Aida, for example" , ""Rigoletto", for example" .)