A carrier on building site cuts short time in plant (8)
I believe the answer is:
asphodel
'plant' is the definition.
(type of flower)
'a carrier on building site cuts short time in' is the wordplay.
'carrier on building site' becomes 'hod' (a hod is used for carrying bricks).
'cuts' means to remove the last letter (I've seen 'cutting' mean this).
'short time' becomes 'spell' (both can mean a short period of time; 'short' indicates a short form).
'in' indicates putting letters inside.
'spell' with its last letter removed is 'spel'.
'hod' going into 'spel' is 'sphodel'.
'a'+'sphodel'='ASPHODEL'
(Other definitions for asphodel that I've seen before include "Flower of lily family - old heaps (anag)" , "liliaceous plant" , "Plant of lily family - lop heads (anag)" , "Shop deal (anag.)" , "blooms from Elysian fields" .)