American punches quiet Hoskins? Pity! (5)
I believe the answer is:
shame
'pity' is the definition.
(synonyms)
'american punches quiet hoskins?' is the wordplay.
'american' becomes 'a' (common abbreviation - e.g. in organisation names).
'punches' indicates putting letters inside (some letters punch a hole in others).
'quiet' becomes 'sh' (both can be said to tell someone to be quiet).
'hoskins?' becomes 'me' (where the crossword setter is 'Hoskins').
'sh'+'me'='shme'
'a' going inside 'shme' is 'SHAME'.
(Other definitions for shame that I've seen before include "pity!" , "Feeling of humiliation" , "Ignomony" , "show up" , "Regrettable thing" .)