Smoothed out on board perhaps (6)
I believe the answer is:
ironed
'smoothed out' is the definition.
(I've seen this in another clue)
'on board perhaps' is the wordplay.
'board' means one lot of letters goes inside another.
'perhaps' becomes 'ired' (I can't justify this - if you can you should give a lot more credence to this answer).
'on' going within 'ired' is 'IRONED'.
Can you help me to learn more?
(Other definitions for ironed that I've seen before include "Smoothed cloth with flatbased implement" , "flattened" , "Smoothed with domestic device" , "Smoothed clothes using heavy object" , "Pressed and smoothed" .)