Dynamic six support conservationists (7)
I believe the answer is:
vibrant
'dynamic' is the definition.
(I've seen this before)
'six support conservationists' is the wordplay.
'six' becomes 'vi' (roman numeral).
'support' becomes 'bra' (a support for the breasts).
'conservationists' becomes 'nt' (abbreviation for National Trust).
'vi'+'bra'+'nt'='VIBRANT'
(Other definitions for vibrant that I've seen before include "Vivacious" , "Aquiver with life and excitement" , "Bright, thrilling or resonant" , "Alive and energetic" , "Strong and vivid" .)