Went in to contribute to the score (6)
I believe the answer is:
twenty
'score' is the definition.
(synonyms)
'went in to contribute to the' is the wordplay.
'in' indicates putting letters inside.
'to contribute' becomes 'y' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'to' means one lot of letters go next to another (I've seen this in other clues).
'the' becomes 't' (the is pronounced as a 't' sound in some dialects).
'y' after 't' is 'ty'.
'went' placed inside 'ty' is 'TWENTY'.
Can you help me to learn more?
(Other definitions for twenty that I've seen before include "Score, XX" , "Hundredweights to a ton" , "previous clue?" , "No longer a teenager" , "John B Keane wrote about many young men of this age" .)