Suddenly start making point in support of English contact sport (5)
I believe the answer is:
erupt
'suddenly start' is the definition.
'erupt' can be an answer for 'start' (erupting is a kind of starting). I am not sure about the 'suddenly' bit.
'point in support of english contact sport' is the wordplay.
'point' becomes 'pt' (abbreviation for point).
'in support of' is a charade indicator (letters next to each other) (in a down clue, some letters hold others up).
'english' becomes 'E' (abbreviation).
'contact sport' becomes 'RU' (rugby union).
'e'+'ru'='eru'
'pt' put after 'eru' is 'ERUPT'.
'making' acts as a link.
Can you help me to learn more?
(Other definitions for erupt that I've seen before include "Suddenly appear" , "Burst forth, like 25" , "Break out dramatically" , "Burst forth violently" , "Blow up like volcano" .)