Starts to observe Ulyssean traits in Bloom (3)
I believe the answer is:
out
'in bloom' is the definition.
(flowers might be in bloom or 'out')
'starts to observe ulyssean traits' is the wordplay.
'starts to' suggests taking the first letters.
The first letters of 'observe ulyssean traits' is 'OUT'.
(Other definitions for out that I've seen before include "Extinguished; abroad" , "Old hat" , "Published; unconscious" , "Not favoured" , "Elsewhere -- unfashionable" .)