Men in exercising also avoid arduous course (3,8)
I believe the answer is:
via dolorosa
'arduous course' is the definition.
(path taken by Jesus on the way to the cross)
'men in exercising also avoid' is the wordplay.
I cannot really understand how this works, but
'men' could be 'or' (military abbreviation for Other Ranks) and 'or' is found in the answer.
an anagram of 'also' is 'losa' which is within the remaining letters.
an anagram of 'avoid' is 'viado' which is within the answer.
No letters remain.
This may be the basis of clue (or it may be nonsense).
(Other definitions for via dolorosa that I've seen before include "Christ's route to Calvary" , "Daunting course of action; route to Calvary" , "Way to Crucifixion" , "Pilgrim's passage" , "Distressing way" .)