Be careful with timepiece, Italian (5,2)
I believe the answer is:
watch it
'be careful' is the definition.
(phrase used to tell someone to be careful)
'with timepiece italian' is the wordplay.
'with' says to put letters next to each other.
'timepiece' becomes 'watch' (watch is a kind of timepiece).
'italian' becomes 'it' (abbreviation for Italian).
'watch' next to 'it' is 'WATCH IT!'.
(Other definitions for watch it that I've seen before include "Be careful!" , "Mind what you say!" , "Mind what you're saying!" , "provide recommendation of film" , "cave!" .)