Flower blooming, nothing less, up on border (5)
I believe the answer is:
tulip
'flower' is the definition.
(tulip is a type of flower)
'blooming nothing less up on border' is the wordplay.
'blooming' becomes 'out' (plants which have bloomed are 'out').
'nothing' becomes 'O' (looks like zero - 0).
'less' suggests deleting specific letters (less can mean minus).
'up' shows that the letters should be reversed in order (in down clue: letters go upwards).
'on border' becomes 'lip' (I've seen this in another clue. I am not sure about the 'on' bit.).
'out' with 'o' removed is 'ut'.
'ut' reversed gives 'tu'.
'tu'+'lip'='TULIP'
Can you help me to learn more?
(Other definitions for tulip that I've seen before include "Flowering bulb (from Amsterdam?)" , "Plant at the centre of the Dutch financial bubble of 1637" , "Spring bulb" , "Bulb producing a single showy flower" , "Dutch bulb?" .)