Shammer’s way to interrupt beggar’s declaration? (8)
I believe the answer is:
impostor
'shammer's' is the definition.
(thesaurus)
'way to interrupt beggar's declaration?' is the wordplay.
'way' becomes 'st' (abbreviation for street).
'to interrupt' indicates putting letters inside.
'beggar's declaration?' becomes 'Impoor' (a beggar might say 'I'm poor').
'st' inserted inside 'impoor' is 'IMPOSTOR'.
(Other definitions for impostor that I've seen before include "deceptive type" , "phoney!" , "False claimant" , "Sit or mop (anag.)" , "type of triumph for Kipling, for example" .)