Current undergarment for a woman lacks opening (4)
I believe the answer is:
eddy
'current' is the definition.
(I know that eddy is a type of current)
'undergarment for a woman lacks opening' is the wordplay.
'undergarment for a woman' becomes 'teddy' (type of undergarment).
'lacks opening' means to remove the first letter (the opening letter is removed).
'teddy' with its initial letter taken away is 'EDDY'.
(Other definitions for eddy that I've seen before include "giddying effect" , "Man" , "Whirling current" , "Christian Scientist" , "Swirl, whirl" .)