Fall back, do, on for support (6)
I believe the answer is:
tripod
'support' is the definition.
(tripod is a kind of support)
'fall back do on' is the wordplay.
'fall' becomes 'trip' (as in tripping over).
'back' says the letters should be written backwards.
'on' says to put letters next to each other.
'do' written backwards gives 'od'.
'trip'+'od'='TRIPOD'
'for' acts as a link.
(Other definitions for tripod that I've seen before include "Drop it (anag)" , "Three-legged support" , "Stand for camera etc" , "support called for" , "Something on three legs" .)