Right behind floating platform (4)
I believe the answer is:
raft
'floating platform' is the definition.
(I've seen this in another clue)
'right behind' is the wordplay.
'right' becomes 'r' (common abbreviation).
'behind' becomes 'aft' (aft means towards or at the end of a ship).
'r'+'aft'='RAFT'
(Other definitions for raft that I've seen before include "... Lots" , "Flat, floating platform" , "Flat water craft; great collection" , "Flat floating craft" , "Structure that floats" .)