Practising again - listen to squeal (10)
I believe the answer is:
rehearsing
'practising' is the definition.
('rehearse' can be a synonym of 'practise')
'again listen to squeal' is the wordplay.
'again' becomes 're' (prefix meaning 'again').
'listen to' becomes 'hear' (to hear something is to listen to it).
'squeal' becomes 'sing' (both can mean to act as an informant).
're'+'hear'+'sing'='REHEARSING'
(Other definitions for rehearsing that I've seen before include "getting ready for a show?" , "Practising (a play)" , "Getting ready for the big night" , "Trying out" , "Preparing for a play" .)