Was in front for less than the whole distance (3)
I believe the answer is:
led
'was in front' is the definition.
(I've seen this in another clue)
'less than the whole distance' is the wordplay.
'less' indicates a hidden word (the clue less some of the letters in it).
'LED' is hidden in the letters of 'than whole distance'.
'for' acts as a link.
(Other definitions for led that I've seen before include "Took by the hand and showed the way" , "showed the way ahead" , "Was guiding" , "Went at the head of others" , "Went first to show the way" .)