The magistrates take note of a point of reference in the survey

'reference in the survey' is the definition.
'bench mark' can be an answer for 'reference' (bench mark is a kind of reference). I am not certain of the 'in the survey' bit.

'the magistrates take note of a point' is the wordplay.
I cannot quite understand how this works, but
'take' could be 'be' (being is a kind of taking) and 'be' is found in the answer.
'note' could be 'mark' (synonyms) and 'mark' is found within the answer.
'point' could be 'n' (N is an example) and 'n' is found in the answer.
The remaining letters 'ch' is a valid word which might be clued in a way I don't see.
This explanation may well be incorrect...

'of' is the link.

Can you help me to learn more?