Draws the line at Australian football (5)
I believe the answer is:
rules
This might be a double definition.
'draws the line' is the first definition.
'rules' can be an answer for 'draws' (ruling is a kind of drawing). I'm not certain of the 'the line' bit.
'australian football' is the second definition.
(I've seen this before)
'at' is the link.
Can you help me to learn more?
(Other definitions for rules that I've seen before include "Conventions" , "following Queensberry?" , "instructions" , "Governs; regulations" , "Regulations, precepts" .)