Pass school regularly (3)
I believe the answer is:
col
'pass' is the definition.
(col is a term for a mountain pass)
'school regularly' is the wordplay.
'regularly' means one should take alternating letters (regularly take one letter, leave next etc.).
The alternate letters of 'school' are 'COL'.
(Other definitions for col that I've seen before include "A pass through ridge" , "route through mountains" , "dip?" , "A depression in mountain range" , "High mountain pass" .)