Iron Man or Lady? (6)
I believe the answer is:
female
'lady?' is the definition.
(lady is a kind of female)
'iron man' is the wordplay.
'iron' becomes 'Fe' (Fe is the chemical symbol for iron).
'man' becomes 'male' ().
'fe'+'male'='FEMALE'
'or' is the link.
(Other definitions for female that I've seen before include "That's what she is" , "A gender" , "On the distaff side" , "Woman or girl" , "Able to bear offspring" .)