One copying standard hill climbing (6)
I believe the answer is:
parrot
'one copying' is the definition.
The answer is a person as well as being a singular noun. This is suggested by the definition.
'standard hill climbing' is the wordplay.
'standard' becomes 'par' (standard of play in golf).
'hill' becomes 'tor' (tor is a kind of hill).
'climbing' says the letters should be written backwards (in a down clue, letters climb up).
'tor' in reverse letter order is 'rot'.
'par'+'rot'='PARROT'
Can you help me to learn more?
(Other definitions for parrot that I've seen before include "Repeat unintelligently" , "Vividly coloured bird" , "Tropical bird noted for mimicking speech" , "Lory" , "Brightly-coloured tropical bird" .)