Useful, extremely, to have bits of advice about flowers (6)
I believe the answer is:
tulips
'flowers' is the definition.
(I've seen this before)
I don't understand the remainder of the clue.
Can you help me to learn more?
(Other definitions for tulips that I've seen before include "Slit up the Spring flowers" , "Garden flowers - tip-toe through them in song" , "plants" , "Garden flowers associated with Amsterdam" , "Flowering bulbs" .)