Swallow part of one attachment (3)
I believe the answer is:
eat
'swallow' is the definition.
(I've seen this in another clue)
'part of one attachment' is the wordplay.
'part of' says the answer is hidden in the clue.
'EAT' is hidden in the letters of 'one attachment'.
(Other definitions for eat that I've seen before include "and 27: Be humiliated" , "Consume for tea" , "Ingest" , "tolerate in diet" , "Use a knife and fork" .)