Half wept to encounter malevolent pest (6)
I believe the answer is:
weevil
'pest' is the definition.
(I've seen this before)
'half wept to encounter malevolent' is the wordplay.
'half' indicates taking half.
'to encounter' says to put letters next to each other.
'malevolent' becomes 'evil' (synonyms).
'wept' cut in half is 'we'.
'we'+'evil'='WEEVIL'
(Other definitions for weevil that I've seen before include "Type of beetle that feeds of stored grain etc" , "Beetle, a grain pest" , "Insect pest that damages crops" , "Small beetle that feeds on plants" , "Insect that feeds on plant products" .)