Climbing a low hill but not to any great extent (2,1,5,5)
I believe the answer is:
on a small scale
'climbing a low hill but not to any great extent' is the definition.
I can't tell whether this defines the answer.
'a low hill but not to any great extent' is the wordplay.
I cannot quite see how this works, but
'a' is found in the answer.
'low' could be 'small' (synonyms) and 'small' is present in the answer.
'not' could be 'o' (I've seen this in other clues) and 'o' is present in the answer.
'extent' could be 'scale' (I've seen this before) and 'scale' is found in the answer.
A single letter 'n' remains which might be clued in a way I don't see.
This explanation may well be incorrect...
Can you help me to learn more?