One taking hill in second/first? (8)
I believe the answer is:
motorist
'one taking' is the definition.
The answer is a person as well as being a singular noun. This is suggested by the definition.
'hill in secondfirst?' is the wordplay.
'hill' becomes 'tor' (tor is a kind of hill).
'in' means one lot of letters goes inside another.
'secondfirst?' becomes 'moist' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'tor' inserted within 'moist' is 'MOTORIST'.
Can you help me to learn more?
(Other definitions for motorist that I've seen before include "One relying on car" , "Traveller" , "One on the road" , "Car-driver" , "Woman taking mini" .)