Whole school allowed to leave, finally (8)
I believe the answer is:
complete
'whole' is the definition.
(similar in meaning)
'school allowed to leave finally' is the wordplay.
'school' becomes 'comp' (short for comprehensive).
'allowed to' becomes 'let' (to let something happen is to allow it).
'finally' suggests the final letters.
The last letter of 'leave' is 'e'.
'comp'+'let'+'e'='COMPLETE'
(Other definitions for complete that I've seen before include "Bring to a finish" , "Having all the necessary parts" , "whole,entire,uncut" , "Finished, entire" , "Perfect - finish" .)