Singer’s first substandard track (5)
I believe the answer is:
spoor
'track' is the definition.
(I know that spoor is a type of trail)
'singer's first substandard' is the wordplay.
'singer's first' becomes 's' (1st letter of 'singer').
'substandard' becomes 'poor' (I've seen this in another clue).
's'+'poor'='SPOOR'
(Other definitions for spoor that I've seen before include "Track of wild animal" , "Animal track or scent" , "24 [TRAIL]" , "Animal track, trail" , "Animal's track or scent" .)