It goes around the edges of gloomy ravine (4)
I believe the answer is:
gyre
'it goes around' is the definition.
The definition suggests a singular noun which matches the answer.
'edges of gloomy ravine' is the wordplay.
'edges of' means to remove the middle letters.
'ravine' becomes 're' (I can't explain this - if you can you should give a lot more credence to this answer).
'gloomy' with its middle removed is 'gy'.
'gy'+'re'='GYRE'
'the' acts as a link.
Can you help me to learn more?
(Other definitions for gyre that I've seen before include "Whirl, spiral" , "Literary circle" , "'A series of concentric circles, as flower petals say (4)'" .)