Essentially unhappy bachelor, lost and disconcerted (7)
I believe the answer is:
abashed
'disconcerted' is the definition.
(abashing is a kind of disconcerting)
'essentially unhappy bachelor lost' is the wordplay.
'essentially' says to take the centre.
'bachelor' becomes 'BA' (Bachelor of Arts).
'lost' becomes 'shed' (I've seen this before).
The middle letter of 'unhappy' is 'a'.
'a'+'ba'+'shed'='ABASHED'
'and' is the link.
(Other definitions for abashed that I've seen before include "Caused to feel uneasy and self-conscious" , "Made ashamed" , "Disconcerted or ashamed" , "Had base (anag.)" , "Stricken with shame" .)