Being alone, I sadly sat in loo (9)
I believe the answer is:
isolation
'being alone' is the definition.
(being isolated or on one's own)
'i sadly sat in loo' is the wordplay.
'sadly' is an anagram indicator.
'sat'+'in'+'loo'='satinloo'
'satinloo' is an anagram of 'solation'.
'i'+'solation'='ISOLATION'
(Other definitions for isolation that I've seen before include "Remoteness" , "State of separation, closing off" , "Separation - solitude" , "Remote and lonely state" , "keeping apart" .)