Port to consume at ten to one for example (5)
I believe the answer is:
ratio
'ten to one for example' is the definition.
(10 to 1 is a ratio)
'port to consume at' is the wordplay.
'port' becomes 'rio' (Rio de Janeiro is a port).
'to consume' is an insertion indicator.
'rio' placed around 'at' is 'RATIO'.
(Other definitions for ratio that I've seen before include "Relation between two things, numbers say" , "One-to-one, maybe" , "Relationship between two amounts" , "Proporation, quantitative relation" , "Measure expressed as a proportion" .)