A swagger, when rounding on a long-distance traveller (9)
I believe the answer is:
astronaut
'long-distance traveller' is the definition.
'astronaut' can be an answer for 'traveller' (astronaut is a kind of traveller). I am not sure about the 'long-distance' bit.
'a swagger when rounding on a' is the wordplay.
'swagger when' becomes 'strut' (both can mean to walk around arrogantly. I am not sure about the 'when' bit.).
'rounding' is an insertion indicator (some letters go round others).
'on'+'a'='ona'
'strut' placed around 'ona' is 'stronaut'.
'a'+'stronaut'='ASTRONAUT'
Can you help me to learn more?
(Other definitions for astronaut that I've seen before include "spaceman" , "Space voyager" , "High-flier" , "heavenly voyager" , "Skier" .)