Starts to see colourful birds giving dirty looks (6)
I believe the answer is:
scowls
'dirty looks' is the definition.
'starts to see colourful birds' is the wordplay.
'starts to' indicates taking the first letters.
'birds' becomes 'owls' (owl is a kind of bird**).
The first letters of 'see colourful' is 'sc'.
'sc'+'owls'='SCOWLS'
'giving' is the link.
(Other definitions for scowls that I've seen before include "Bad-tempered frowns" , "Angry frowns" , "Frowns with displeasure" , "Gives black looks" , "Furrows forehead in bad humour" .)