Blue soil at end of rockery (6)
I believe the answer is:
earthy
'blue' is the definition.
(both can mean sexual)
'soil at end of rockery' is the wordplay.
'soil' becomes 'earth' (synonyms).
'at end of' suggests the final letters.
The last letter of 'rockery' is 'y'.
'earth'+'y'='EARTHY'
(Other definitions for earthy that I've seen before include "Crude - vulgar" , "grubby" , "Like soil; uninhibitedly direct" , "Coarse as humour may be" , "Resembling soil" .)