( informal ) used to say that sb notices every opportunity to gain an advantage
HE, SHE, ETC. DOESN'T MISS A TRICK
Meaning of HE, SHE, ETC. DOESN'T MISS A TRICK in English
Oxford Advanced Learner's English Dictionary. Оксфордский английский словарь для изучающик язык на продвинутом уровне. 2005