For an airman, look in a mine! (5)
I believe the answer is:
pilot
'for an airman' is the definition.
(pilot is a kind of airman)
'look in a mine' is the wordplay.
'look' becomes 'lo' ('lo' is an archaic exclamation meaning 'look!').
'in' indicates putting letters inside.
'a mine' becomes 'pit' (down the pit).
'lo' put within 'pit' is 'PILOT'.
(Other definitions for pilot that I've seen before include "Guide (e.g. of ship through harbour)" , "Navigator" , "One who brings a vessel into port" , "Plane flyer" , "Guide - flier" .)