Bachelors, I see, are essential (5)
I believe the answer is:
basic
'essential' is the definition.
(similar in meaning)
'bachelors i see' is the wordplay.
'bachelors' becomes 'bas' (people with Bachelor of Arts degrees).
'see' becomes 'C' (the word for the letter, according to Chambers).
'bas'+'i'+'c'='BASIC'
'are' is the link.
(Other definitions for basic that I've seen before include "Introductory" , "Radical" , "No-frills" , "At the simplest level" , "Straightforward" .)