Spice Girl appears in rank undergarments (8)
I believe the answer is:
lingerie
'undergarments' is the definition.
(I have seen 'Slinky undergarments' mean 'lingerie' so perhaps 'undergarments' could also mean 'lingerie')
'spice girl appears in rank' is the wordplay.
'spice girl' becomes 'geri' (Geri Halliwell).
'appears in' means one lot of letters goes inside another.
'rank' becomes 'line'.
'geri' put into 'line' is 'LINGERIE'.
(Other definitions for lingerie that I've seen before include "Women's underclothes" , "Slinky undergarments" , "Scanties" , "flimsy stuff" , "Female underwear" .)