The mug I sent broken (5)
I believe the answer is:
stein
'the mug' is the definition.
(stein is a kind of mug)
'i sent broken' is the wordplay.
'broken' indicates anagramming the letters.
'i'+'sent'='isent'
'isent' is an anagram of 'STEIN'.
(Other definitions for stein that I've seen before include "Beer-mug" , "Earthenware beer jug" , "Inset (anag.)" , "Gertrude ---; US writer" , "Inset into earthenware mug for beer" .)