Fragrant gum resin (5)
I believe the answer is:
'fragrant gum resin' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for myrrh that I've seen before include "Aromatic resin" , "Famous gift" , "The Three Wise Men brought Jesus gifts of gold, frankincense and . . . . ." , "Aromatic gum" , "Fragrant gum resin" .)