American chap pinches gold, having no principles (6)
I believe the answer is:
amoral
'having no principles' is the definition.
(having no moral principles)
'american chap pinches gold' is the wordplay.
'american' becomes 'a' (common abbreviation - e.g. in organisation names).
'chap' becomes 'mal' ().
'pinches' is an insertion indicator (pinch can mean to steal).
'gold' becomes 'or' ('or' is the heraldic name for gold).
'mal' placed around 'or' is 'moral'.
'a'+'moral'='AMORAL'
(Other definitions for amoral that I've seen before include "Without moral standards or principles" , "Unconcerned about what's right or wrong" , "Lacking any ethical sense" , "outrageous!" , "Unconcerned with correctness" .)