Leave half of the side section (6)
I believe the answer is:
depart
'leave' is the definition.
(I know that depart is a more specific form of leave)
'half of the side section' is the wordplay.
'half of' indicates taking half.
'section' becomes 'part' (synonyms).
'side' halved is 'de'.
'de'+'part'='DEPART'
(Other definitions for depart that I've seen before include "Leave (6)" , "Prated (anag.)" , "Start out" , "Quit" , "Set out" .)