It's blooming newspaper floating on river? (9)
I believe the answer is:
sunflower
'it's blooming' is the definition.
(a plant that blooms)
'newspaper floating on river?' is the wordplay.
'newspaper' becomes 'sun' (UK newspaper The Sun).
'floating on' says to put letters next to each other (in a down clue, some letters go on top of others).
'river?' becomes 'flower' (a river flows).
'sun'+'flower'='SUNFLOWER'
(Other definitions for sunflower that I've seen before include "that Van Gogh used to paint" , "Plant's" , "Large golden bloom" , "nickname of US State" , "Tall plant" .)