Fool about any steep gully! (6)
I believe the answer is:
canyon
'steep gully' is the definition.
'canyon' can be an answer for 'gully' (I've seen this before). I am unsure of the 'steep' bit.
'fool about any' is the wordplay.
'fool' becomes 'con' (I've seen this in another clue).
'about' is an insertion indicator.
'con' going around 'any' is 'CANYON'.
Can you help me to learn more?
(Other definitions for canyon that I've seen before include "A deep gorge with a river, may be Grand" , "Narrow steep-sided valley" , "Ravine formed by a river" , "The Grand . . . . . . of Colorado is a natural phenomenon in USA" , "gully" .)