Trainer asleep I gathered before start of race (8)
I believe the answer is:
espalier
'trainer' is the definition.
(frame for training a plant)
'asleep i gathered before start of race' is the wordplay.
'gathered' indicates an anagram.
'before' is a charade indicator (letters next to each other).
'start of' suggests taking the first letters.
The first letter of 'race' is 'r'.
'asleep'+'i'='asleepi'
'asleepi' anagrammed gives 'espalie'.
'espalie'+'r'='ESPALIER'
(Other definitions for espalier that I've seen before include "Lattice-work for tree-training" , "Wood used for lattice work" , "Trellis on which shrubs are trained, like pearlies" , "Fruit tree that grows flat against the wall" , "Lattice for growing plants" .)