Adorn the sides of bridge and platform (6)
I believe the answer is:
bedeck
'adorn' is the definition.
(I know that bedeck is a type of adorn)
'sides of bridge and platform' is the wordplay.
'sides of' suggests removing the centre (only the letters on the sides remain).
'and' says to put letters next to each other.
'platform' becomes 'deck' (deck is a kind of platform).
'bridge' with its centre taken out is 'be'.
'be'+'deck'='BEDECK'
'the' acts as a link.
(Other definitions for bedeck that I've seen before include "Festoon; decorate" , "Adorn, cover with decorations" , "Festoon, adorn" , "Trim" , "Lavishly decorate" .)