Pest controller putting some bitumen all over (3,4)
I believe the answer is:
rat trap
'pest controller' is the definition.
(I've seen this before)
'some bitumen all over' is the wordplay.
'some' becomes 'part' (only part of something).
'bitumen' becomes 'tar' (tar is a kind of bitumen).
'all over' says the letters should be written backwards.
'part'+'tar'='parttar'
'parttar' backwards is 'RAT-TRAP'.
'putting' acts as a link.
(Other definitions for rat trap that I've seen before include "might this stop his desertion?" , "in which pest caught" , "rodent catcher" , "pest controller" , "snare for vermin" .)