Former runner Steve to study intensively (4)
I believe the answer is:
cram
'study intensively' is the definition.
(I've seen this before)
'former runner steve' is the wordplay.
I cannot really understand how this works, but
'runner' could be 'r' (abbreviation for river) and 'r' is found within the answer.
The remaining letters 'cam' is a valid word which might be clued in a way I don't understand.
This may be the basis of clue (or it may be nonsense).
'to' acts as a link.
Can you help me to learn more?
(Other definitions for cram that I've seen before include "Study hard for exam" , "Feed greedily" , "jam" , "Stuff full" , "Crowd or pack to capacity" .)