Manufacturer of stock line of game that's inconclusive (3)
I believe the answer is:
oxo
'manufacturer of stock' is the definition.
'oxo' can be an answer for 'stock' (stock for cooking can be made from Oxo cubes). I'm not certain of the 'manufacturer of' bit.
'line of game that's inconclusive' is the wordplay.
'line of' becomes 'ox' (I can't justify this - if you can you should believe this answer much more).
'game' becomes 'on' (both can mean willing).
'that's inconclusive' means to remove the last letter.
'on' with its final letter taken off is 'o'.
'ox'+'o'='OXO'
Can you help me to learn more?
(Other definitions for oxo that I've seen before include "Stock cube brand" , "Proprietary brand of beef cube" .)