I’m going now to pick up the centrepiece for swish headdress (5)
I believe the answer is:
tiara
'headdress' is the definition.
(tiara is a kind of headdress)
'i'm going now to pick up the centrepiece for swish' is the wordplay.
'i'm' becomes 'i' (I've seen this in other clues).
'going now' becomes 'tar' (I can't explain this - if you can you should believe this answer much more).
'to pick up' means one lot of letters goes inside another.
'the centrepiece for' indicates the central letters.
'swish' becomes 'lap' (synonyms).
The middle letter of 'lap' is 'a'.
'i' put inside 'tar' is 'tiar'.
'tiar'+'a'='TIARA'
Can you help me to learn more?
(Other definitions for tiara that I've seen before include "Jewelled crescent-shaped headdress" , "High diadem" , "Decorative headband" , "Woman's headdress for very formal occasions" , "Top decoration" .)