Crazy: equipment almost entirely for a song (8)
I believe the answer is:
madrigal
'a song' is the definition.
(madrigal is a kind of song)
'crazy equipment almost entirely' is the wordplay.
'crazy' becomes 'mad' (synonyms).
'equipment' becomes 'rig' (rig is a kind of equipment).
'almost' means to remove the last letter (most of the word but not all of it).
'entirely' becomes 'all' (I've seen this before).
'all' with its last letter taken off is 'al'.
'mad'+'rig'+'al'='MADRIGAL'
'for' is the link.
(Other definitions for madrigal that I've seen before include "Unaccompanied harmonised part song" , "air" , "Elizabethan song" , "Drag Liam around to hear an unaccompanied song" , "glee" .)