Religious education is included in climb (4)
I believe the answer is:
rise
'climb' is the definition.
('rise' can be a synonym of 'climb')
'religious education is included' is the wordplay.
'religious education' becomes 're'.
'included' indicates putting letters inside.
're' enclosing 'is' is 'RISE'.
'in' acts as a link.
(Other definitions for rise that I've seen before include "To swell (bread)" , "Go up" , "Get out of bed, sire" , "Ascent" , "Ascend" .)