Show off garter, skirt and tank-top in X (10)
I believe the answer is:
grandstand
'show off' is the definition.
(I've seen this before)
'garter skirt and tank-top in x' is the wordplay.
'skirt' says to hollow out the word (remove centre letters) (skirt can mean the edge or outside of something).
'tank-top' becomes 't' (top of the word 'tank-').
'in' is an insertion indicator.
'x' becomes 'sand' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'garter' with its centre removed is 'gr'.
't' placed within 'sand' is 'stand'.
'gr'+'and'+'stand'='GRANDSTAND'
Can you help me to learn more?
(Other definitions for grandstand that I've seen before include "Main area for race spectators" , "Racecourse construction" , "Terraced block of seats commanding the best view of a sporting event" , "Play to the audience" , "From which spectators watch" .)