Recognise the boil (6)
I believe the answer is:
seethe
'boil' is the definition.
(I know that boil can be written as seethe)
'recognise the' is the wordplay.
'recognise' becomes 'see' (both can mean to notice).
'see'+'the'='SEETHE'
(Other definitions for seethe that I've seen before include "Be filled with intense but unexpressed anger" , "Bubble gently like boiling water" , "become agitated" , "Simmer with anger" , "(Of liquid) move as if boiling" .)