Stand for one reading in John's gospel? (5)
I believe the answer is:
brook
'stand for' is the definition.
(I've seen this before)
'one reading in john's gospel?' is the wordplay.
'one reading' becomes 'r' (one of the traditional three R's of education).
'in' indicates putting letters inside.
'john's gospel?' becomes 'book' (John's gospel is an example).
'r' going within 'book' is 'BROOK'.
(Other definitions for brook that I've seen before include "Allow" , "Stand for" , "running water" , "stomach" , "Small fresh-water stream" .)