Woman takes it to be crucial (5)
I believe the answer is:
vital
'be crucial' is the definition.
(I've seen this in another clue)
'woman takes it' is the wordplay.
'woman' becomes 'val' (val is a name for a woman).
'takes' is an insertion indicator.
'val' going around 'it' is 'VITAL'.
'to' acts as a link.
(Other definitions for vital that I've seen before include "Characteristic of life" , "Energetic - displaying life" , "Essential for life; key" , "Desperately important" , "Critical; life-sustaining" .)