Shriek catching a young man dressing (5,5)
I believe the answer is:
salad cream
'dressing' is the definition.
(I know that salad cream is a type of dressing)
'shriek catching a young man' is the wordplay.
'shriek' becomes 'scream' (synonyms).
'catching' indicates putting letters inside.
'young man' becomes 'lad' (lad can mean a boy or young man).
'a'+'lad'='alad'
'scream' going around 'alad' is 'SALAD CREAM'.
(Other definitions for salad cream that I've seen before include "Sauce" , "Dressing like mayonnaise" .)