Detect in wrong act and uncertain touch (5,3)
I believe the answer is:
catch out
'detect' is the definition.
(catching out is a kind of detecting)
'wrong act and uncertain touch' is the wordplay.
'wrong' indicates an anagram.
'and' means one lot of letters go next to another.
'uncertain' indicates an anagram.
'act' with letters rearranged gives 'cat'.
'touch' with letters rearranged gives 'chout'.
'cat'+'chout'='CATCH OUT'
'in' is the link.
(Other definitions for catch out that I've seen before include "Detect in a mistake - gotcha" , "Detect in a mistake or deceit" , "detect in error" , "Trap" .)