What the poilu has to put on his hair (3)
I believe the answer is:
oil
'put on his hair' is the definition.
The answer and definition can be both to do with contact as well as being verbs in their base form.
Perhaps they are linked in a way I don't understand?
'what the poilu has' is the wordplay.
'has' says the answer is hidden in the clue.
'OIL' is hidden in the letters of 'what poilu'.
'to' is the link.
Can you help me to learn more?
(Other definitions for oil that I've seen before include "SECOND PART OF 23" , "eg Olive" , "Lubricant or petroleum" , "Grease" , "Crude" .)