Yankee on Wednesday returned, in early morning, damp? (4)
I believe the answer is:
dewy
'in early morning damp?' is the definition.
'yankee on wednesday returned' is the wordplay.
'yankee' becomes 'y' (phonetic alphabet: alpha, bravo, charlie etc.).
'on' says to put letters next to each other.
'wednesday' becomes 'wed' ('Wed' can be a synonym of 'wednesday').
'returned' says the letters should be written in reverse.
'wed' in reverse letter order is 'dew'.
'y' after 'dew' is 'DEWY'.
(Other definitions for dewy that I've seen before include "Wet with condensation" , "fresh in the morning?" , "wet grass" , "Fresh early on" , "laden with pearls" .)