Wave put in the hair (6)
I believe the answer is:
roller
'wave put in the hair' is the definition.
'roller' can be an answer for 'wave' (I've seen this before). I am not sure about the 'put in the hair' bit.
'wave put in the' is the wordplay.
'wave' becomes 'roll' (roll is a kind of wave).
'put' means one lot of letters go next to another.
'in the' becomes 'er' (I can't justify this - if you can you should give a lot more credence to this answer).
'roll'+'er'='ROLLER'
Can you help me to learn more?
(Other definitions for roller that I've seen before include "Cylinder for lawn etc" , "road maintenance vehicle" , "Painting tool" , "flattens lawn" , "Flattener for grass" .)