It enables one to get an angle on the situation (10)
I believe the answer is:
theodolite
'situation' is the definition.
Although both the answer and definition are singular nouns, I don't understand how one could define the other.
'it enables one to get an angle on the' is the wordplay.
I cannot really understand how this works, but
'it' could be 't' (abbreviation. e.g. in 'tis) and 't' is present in the answer.
'one' could be 'li' (I've seen this in other clues) and 'li' is found in the answer.
'the' could be 't' (the is pronounced as a 't' sound in some dialects) and 't' is found in the answer.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for theodolite that I've seen before include "Surveyor's instrument" , "transit, in America" , "What a surveyor might use" , "Surveying instrument" .)