Sign he has dropped out of the race (5)
I believe the answer is:
trace
'sign' is the definition.
(thesaurus)
'the race' is the wordplay.
'the' becomes 't' (the is pronounced as a 't' sound in some dialects).
't'+'race'='TRACE'
'he has dropped out of' acts as a link.
This may not be right. Some or all of it may be part of another bit of the clue.
Can you help me to learn more?
(Other definitions for trace that I've seen before include "Discover - modicum" , "Vestige; manage to find" , "Evidence" , "Track; small quantity" , "Detect - track" .)