I have to chase rascal and fool showing no emotion (9)
I believe the answer is:
impassive
'showing no emotion' is the definition.
(I've seen this before)
'i have to chase rascal and fool' is the wordplay.
'i have' becomes 'I've' (contraction of 'I have').
'to chase' says to put letters next to each other (some letters chase after others).
'rascal' becomes 'imp' (synonyms).
'and' means one lot of letters go next to another.
'fool' becomes 'ass' (both can mean a stupid person).
'imp'+'ass'='impass'
'ive' after 'impass' is 'IMPASSIVE'.
(Other definitions for impassive that I've seen before include "Inscrutable, not showing emotion" , "unmoved" , "Not showing emotions in face" , "unfeeling" , "poker-faced" .)