Sense of proportion needed in arbitration (5)
I believe the answer is:
ratio
'sense of proportion' is the definition.
'ratio' can be an answer for 'proportion' (I've seen this in other clues). I'm unsure of the 'sense of' bit.
'in arbitration' is the wordplay.
'in' indicates the answer is hidden within the clue.
'RATIO' is hidden within 'arbitration'.
'needed' is the link.
Can you help me to learn more?
(Other definitions for ratio that I've seen before include "Proportional relation between two numbers" , "Mathematical relationship" , "E.g. two to one" , "One to one - maybe" , "Proportion, relationship" .)