Relationship held in admiration (5)
I believe the answer is:
ratio
'relationship' is the definition.
(relationship between two numbers)
'held in admiration' is the wordplay.
'held in' indicates a hidden word.
'RATIO' can be found hidden inside 'admiration'.
(Other definitions for ratio that I've seen before include "Proportional relation between two numbers" , "figures in relationship" , "Quotient, proportion" , "Quotient of two numbers" , "Proportional relationship" .)