If you want to make a splash, try rolling on it! (3)
I believe the answer is:
log
'if you want to' is the definition.
I can't judge whether this definition defines the answer.
'a splash try rolling on it' is the wordplay.
'a splash' becomes 'l' (I am not sure about this - if you are sure you should believe this answer much more).
'try' becomes 'go' (both can mean an attempt).
'rolling' says the letters should be written backwards.
'on it' is a charade indicator (letters next to each other).
'go' in reverse letter order is 'og'.
'l'+'og'='LOG'
'make' acts as a link.
Can you help me to learn more?
(Other definitions for log that I've seen before include "Nautical record in timber?" , "Piece of cut wood" , "Sea captain's diary of voyage" , "number in maths class?" , "Lump of wood or ship's diary" .)