One caught in face, the whole thing seen in theatre (5,4)

I haven't cracked this one yet — but the brilliant team at Times for the Times have:

I (one) + C (caught) contained by [in] MUSH (face), ALL (the whole thing).’ Mush’ is slang for mouth or face, but either way it has to be pronounced ‘moosh’ as in ‘push’, not ‘mush’ as in ‘hush’.