Complete section of boxing match gets cancelled (5,3)

I believe the answer is:

round off

I'm a little stuck... Click here to teach me more about this clue!

'complete' is the definition.
The definition and answer can be both related to change as well as being verbs in their base form.
Perhaps they are linked in a way I don't understand?

'section of boxing match gets cancelled' is the wordplay.
'section of boxing match' becomes 'round' (I can't justify this - if you can you should believe this answer much more).
'gets' means one lot of letters go next to another.
'cancelled' becomes 'off' (similar in meaning).
'round'+'off'='ROUND OFF'

Can you help me to learn more?

(Other definitions for round off that I've seen before include "finish" , "Conclude" .)

Want a hint initially instead of a full solution? Install my app