A frustrating repeat, but now we leave with a profit (4,2,2,5)
I believe the answer is:
here we go again
'a frustrating repeat' is the definition.
(phrase said in frustration)
'now we leave with a profit' is the wordplay.
'now' becomes 'here' (I've seen this before).
'leave with' becomes 'goa' (I can't justify this - if you can you should give a lot more credence to this answer).
'a profit' becomes 'gain' (synonyms).
'here'+'we'+'goa'+'gain'='HERE WE GO AGAIN'
'but' is the link.
Can you help me to learn more?
(Other definitions for here we go again that I've seen before include "The same thing is reoccurring! (colloq.)" , "The same undesirable things are happening" , "The same situation is recurring" , "Oh no, the same old nonsense" , "Leaving for our regular holiday" .)