Unusual tip to stop theft showing over-attention to detail (3-7)
I believe the answer is:
nit-picking
'over-attention to detail' is the definition.
(nit-picking means pedantry)
'unusual tip to stop theft' is the wordplay.
'unusual' indicates anagramming the letters.
'to stop' is an insertion indicator.
'theft' becomes 'nicking' (nick can informally mean to steal).
'tip' anagrammed gives 'tpi'.
'tpi' placed inside 'nicking' is 'NIT-PICKING'.
'showing' acts as a link.
(Other definitions for nit-picking that I've seen before include "Over-scrupulous" , "activity of school nurse?" .)