Relationship from a little time in Brazilian city (5)
I believe the answer is:
ratio
'relationship' is the definition.
(relationship between two numbers)
'a little time in brazilian city' is the wordplay.
'little time' becomes 't' (abbreviation for time).
'in' is an insertion indicator.
'brazilian city' becomes 'Rio' (Rio de Janeiro).
'a'+'t'='at'
'at' inserted within 'rio' is 'RATIO'.
'from' acts as a link.
(Other definitions for ratio that I've seen before include "Proportion between two numbers" , "Percentage" , "Measure of two relative sizes" , "Relation between two amounts" , "Relationship between two numerical quantities" .)