One so delayed originally desperately lonely (8)
I believe the answer is:
isolated
'lonely' is the definition.
(I've seen this before)
'one so delayed originally desperately' is the wordplay.
'one' becomes 'i' (Roman numeral).
'delayed' becomes 'late' (running late).
'originally' says to take the initial letters.
The initial letter of 'desperately' is 'd'.
'i'+'so'+'late'+'d'='ISOLATED'
(Other definitions for isolated that I've seen before include "Placed apart from others" , "hard to find" , "Divorced" , "Cut off or left behind" , "Off the beaten track" .)