Union line upset about to bloom (5)
I believe the answer is:
tulip
'bloom' is the definition.
The definition and answer can be both plants as well as being singular nouns.
Maybe they are linked in a way I don't understand?
'union line upset about' is the wordplay.
'union' becomes 'U' (common abbreviation as in Trades Union Congress).
'line' becomes 'l' (used when specifying particular lines from a poem).
'upset' becomes 'tip' (I've seen this in another clue).
'about' means one lot of letters goes inside another.
'u'+'l'='ul'
'ul' placed into 'tip' is 'TULIP'.
'to' acts as a link.
Can you help me to learn more?
(Other definitions for tulip that I've seen before include "It blooms in 11 down" , "Spring bulb" , "Spring-flowering plant" , "Popular garden flower from Amsterdam?" , "Plant of the lily family with a single showy flower" .)