Get on with any number in English school (7)
I believe the answer is:
entrain
'get on' is the definition.
(entraining is a kind of getting on)
'any number in english school' is the wordplay.
'any number' becomes 'n' (mathematical symbol for an unspecified number).
'in' means one lot of letters goes inside another.
'english' becomes 'E' (abbreviation).
'school' becomes 'train' (training is a kind of schooling).
'e'+'train'='etrain'
'n' going into 'etrain' is 'ENTRAIN'.
'with' is the link.
(Other definitions for entrain that I've seen before include "board the Orient Express?" , "Board a rail service" , "Bring about as consequence" , "Board carriage" , "Get on board railway carriages" .)