Lad upset about angry travellers (6)
I believe the answer is:
nomads
'travellers' is the definition.
(nomad is a kind of traveller)
'lad upset about angry' is the wordplay.
'lad' becomes 'son' (lad can informally mean a young boy).
'upset' says the letters should be written backwards.
'about' means one lot of letters goes inside another.
'angry' becomes 'mad' (similar in meaning).
'son' in reverse letter order is 'nos'.
'nos' going around 'mad' is 'NOMADS'.
(Other definitions for nomads that I've seen before include "Wandering people, roaming tribes" , "Travellers" , "They travel from place to place seeking food and pasture" , "They wander" , "Damson for wandering tribes" .)