Good books on top Garda in southeast - the one investigating what's going on along the canal (8)
I believe the answer is:
otoscope
'one investigating what's going on along the canal' is the definition.
Although both the answer and definition are singular nouns, I don't understand how one could define the other.
'good books on top garda in southeast' is the wordplay.
'good books' becomes 'ot' (abbreviation for Old Testatment).
'top' indicates taking the first letters.
'garda in southeast' becomes 'scope' (I can't justify this - if you can you should give a lot more credence to this answer).
The first letter of 'on' is 'o'.
'ot'+'o'+'scope'='OTOSCOPE'
'the' is the link.
Can you help me to learn more?
(Other definitions for otoscope that I've seen before include "Instrument for inspecting ears" , "Lug instrument" , "instrument coming close to a canal" , "Instrument for visual examination of an ear" , "It's used to examine the ear" .)