Spiral shaped lilac given to ambassador (7)
I believe the answer is:
helical
'spiral' is the definition.
('helical' can be a synonym of 'spiral')
'shaped lilac given to ambassador' is the wordplay.
'shaped' is an anagram indicator.
'given to' means one lot of letters go next to another.
'ambassador' becomes 'he' (His or Her Excellency).
'lilac' anagrammed gives 'lical'.
'lical' put after 'he' is 'HELICAL'.
(Other definitions for helical that I've seen before include "In the form of a spiral" , "Like the pattern on a snail's shell" , "Like a spiral or spring" , "Spiral-shaped" , "Curled like corkscrew" .)