The row brewing over foreign currency won't improve things (6)
I believe the answer is:
worsen
'improve things' is the definition.
'worsen' can be an answer for 'improve' (thesaurus). I am not certain of the 'things' bit.
'the row brewing over foreign currency won't' is the wordplay.
I cannot quite understand how this works, but
an anagram of 'row' is 'wor' which is within the answer.
'foreign currency' could be 'sen' (I've seen this in another clue) and 'sen' is found within the answer.
This accounts for all the letters.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for worsen that I've seen before include "Go to pot" , "go downhill" , "Aggravate" , "Become more inferior" , "Become less well" .)