It's an honour to enter the Royal Society in such garments (5)
I believe the answer is:
robes
'such garments' is the definition.
'robes' can be an answer for 'garments' (robing is a kind of garmenting). I am not sure about the 'such' bit.
'it's an honour to enter the royal society' is the wordplay.
'it's an honour' becomes 'obe' (Order of the British Empire award).
'to enter' indicates putting letters inside.
'the royal society' becomes 'rs'.
'obe' inserted inside 'rs' is 'ROBES'.
'in' is the link.
Can you help me to learn more?
(Other definitions for robes that I've seen before include "Ceremonial clothing" , "Gowns" , "'The 19 across 1 across' of the French Revolution" , "Long loose flowing garments" , "Official vestments" .)