In time, some fares must go up (3)
I believe the answer is:
era
'in time' is the definition.
'era' can be an answer for 'time' (an era is a period of time). I am not sure about the 'in' bit.
'some fares must go up' is the wordplay.
'some' indicates a hidden word (some parts of the word are used).
'must go up' is a reversal indicator.
'are' is hidden within 'fares'.
'are' backwards is 'ERA'.
Can you help me to learn more?
(Other definitions for era that I've seen before include "Geological age" , "Characteristic period" , "Special time" , "Period of alteration" , "Aeon" .)