Woman of immense value
I believe the answer is:
eva
'woman' is the definition.
(woman's name)
'of immense value' is the wordplay.
'of' indicates the answer is hidden within the clue.
'EVA' is hidden in the letters of 'immense value'.
(Other definitions for eva that I've seen before include "girl appears" , "-- Cassidy, singer, 1963-96" , "Girl's name; space walk" , "Miss Peron, perhaps" , "Braun or Peron, say" .)