Wag hiding in school, behind big dipper? (10)
I believe the answer is:
switchback
'dipper?' is the definition.
(I have seen 'big dipper' mean 'switchback' so perhaps 'dipper' could also mean 'switchback')
'wag hiding in school behind big' is the wordplay.
'wag' becomes 'wit' (synonyms).
'hiding in' indicates putting letters inside.
'school' becomes 'sch' (abbreviation).
'behind big' becomes 'back' (I can't explain this - if you can you should believe this answer much more).
'wit' placed inside 'sch' is 'switch'.
'switch'+'back'='SWITCHBACK'
Can you help me to learn more?
(Other definitions for switchback that I've seen before include "big dipper" , "ups and downs" , "roller coaster" , "Up-and-down road" , "uneven way" .)