Exercises aviators, requiring no indication of excellence necessarily (8)
I believe the answer is:
perforce
'necessarily' is the definition.
(thesaurus)
'exercises aviators requiring no indication of excellence' is the wordplay.
I cannot quite see how this works, but
'exercises' could be 'pe' and 'pe' is located in the answer.
'no' could be 'o' (resembles 0 - 'no' can mean 'zero') and 'o' is located in the answer.
This may be the basis of clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for perforce that I've seen before include "without choice" , "willy-nilly" , "Necessarily, arising from free crop" , "Of necessity" , "Old word for necessarily, due to circumstances" .)