Spilt beer on top of the hat (5)
I believe the answer is:
beret
'hat' is the definition.
(I've seen this before)
'spilt beer on top of the' is the wordplay.
'spilt' indicates anagramming the letters.
'on top of' suggests taking the first letters.
The initial letter of 'the' is 't'.
'beer' with letters rearranged gives 'bere'.
'bere'+'t'='BERET'
(Other definitions for beret that I've seen before include "Flattish round hat" , "Military cap" , "Soft round cap without a peak" , "Soft peak-less kind of cap" , "Cap with no brim" .)