Bachelor takes the plunge (5)
I believe the answer is:
bathe
'plunge' is the definition.
(I've seen this before)
'bachelor takes the' is the wordplay.
'bachelor' becomes 'BA' (the qualification: Bachelor of Arts).
'takes' says to put letters next to each other.
'ba'+'the'='BATHE'
(Other definitions for bathe that I've seen before include "Take dip in sea" , "Steep" , "Swim in sea" , "Immerse oneself in water" , "Take a swim; envelop" .)