Zacsmaster, It is not ignored at all.
Every cryptic clue has two parts
a) A straight definition
b) The wordplay leading to the an answer which meets the definition.
The straight definition is always at the very start or at the very end of the clue so in this question, we were either looking for a word that was RUBBER or was ROUND
In this case it was Rubber. Sorbo is a spongy type of rubber.
The wordplay leads to the same answer by the following reasoning
ball = ORB
so = SO
round = around
SO placed around ORB gives SORBO (the rubber)
As a postscript I might add that the straight definition is sometimes chosen to mislead so fo example a FLOWER may be either a bloom or a river (it flows).