Strict and clear ruling ultimately Italy breaks (5)
I believe the answer is:
rigid
'strict' is the definition.
(synonyms)
'clear ruling ultimately italy breaks' is the wordplay.
'clear' becomes 'rid' (synonyms).
'ultimately' suggests the final letters.
'italy' becomes 'i'.
'breaks' indicates putting letters inside.
The final letter of 'ruling' is 'g'.
'g'+'i'='gi'
'rid' placed around 'gi' is 'RIGID'.
'and' acts as a link.
(Other definitions for rigid that I've seen before include "Stiff, unbending" , "starched too much?" , "Stiff and inflexible" , "Frozen" , "Hard" .)