Fliers with time to construct a floating platform (4)
I believe the answer is:
raft
'a floating platform' is the definition.
(I've seen this before)
'fliers with time' is the wordplay.
'fliers' becomes 'RAF' (Royal Air Force).
'with' says to put letters next to each other.
'time' becomes 't' (abbreviation).
'raf'+'t'='RAFT'
'to construct' is the link.
(Other definitions for raft that I've seen before include "Floating mass of logs" , "Primitive boat" , "Structure made of timber" , "Makeshift boat" , "Wooden craft" .)