Was first, maybe if not in the field (3)
I believe the answer is:
led
'was first' is the definition.
'maybe if not in the field' is the wordplay.
'maybe' indicates an anagram.
'not in the' suggests deleting specific letters.
'field' with 'if' taken away is 'eld'.
'eld' anagrammed gives 'LED'.
(Other definitions for led that I've seen before include "Was guiding" , "Light-emitting diode (abbr.)" , "Guided; small light" , "Came first" , "Paved the way" .)