Not totally great beginning to Olympic movement (5)
I believe the answer is:
largo
'movement' is the definition.
(largo is a kind of movement)
'not totally great beginning to olympic' is the wordplay.
'not totally' means to remove the last letter.
'great' becomes 'large' (similar in meaning).
'beginning to' indicates taking the first letters.
The initial letter of 'olympic' is 'o'.
'large' with its final letter taken off is 'larg'.
'larg'+'o'='LARGO'
(Other definitions for largo that I've seen before include "moving slowly" , "Goldfinger part" , "Broad and slow (mus.)" , "To be played slowly and broadly" , "Mus. slow movement" .)