The Scotsman saw off the birds (6)
I believe the answer is:
macaws
'the birds' is the definition.
(macaw is a kind of bird)
'the scotsman saw off' is the wordplay.
'the scotsman' becomes 'mac'.
'off' is an anagram indicator.
'saw' is an anagram of 'aws'.
'mac'+'aws'='MACAWS'
(Other definitions for macaws that I've seen before include "Long-tailed parrots of Central and South America" , "Birds" , "Long-tailed, brilliantly-coloured parrots" , "More than one bird" , "Brightly-coloured parrots" .)