Leader seen in tent beside track (3,3)
I believe the answer is:
top dog
'leader' is the definition.
(I know that top dog is a type of leader)
'tent beside track' is the wordplay.
'tent' becomes 'top' (top is a kind of tent).
'beside' means one lot of letters go next to another (I've seen this in other clues).
'track' becomes 'dog' (synonyms).
'top'+'dog'='TOP DOG'
'seen in' acts as a link.
(Other definitions for top dog that I've seen before include "Dominant individual" , "Thirteen [HONCO]" , "Supremo or master canine" , "high in the sky?" , "Master or victor of canine hue" .)