Laugh with Republican over Friends character's instrument (9)
I believe the answer is:
harmonica
'instrument' is the definition.
(I know that harmonica is a type of free-reed instrument)
'laugh with republican over friends character's' is the wordplay.
'laugh' becomes 'ha'.
'with' says to put letters next to each other.
'republican' becomes 'r' (abbreviation).
'over' means one lot of letters go next to another (in a down clue, some letters go over others).
'friends character' becomes 'monica' (I've seen this in another clue).
'ha'+'r'+'monica'='HARMONICA'
(Other definitions for harmonica that I've seen before include "It's played by blowing into holes" , "Mouth organ" , "glasses of water" , "Small wind instrument" , "Harp" .)