Cross Tiber, rail having been mended (9)
I believe the answer is:
irritable
'cross' is the definition.
(I've seen this in another clue)
'tiber rail having been mended' is the wordplay.
'having been mended' indicates anagramming the letters.
'tiber'+'rail'='tiberrail'
'tiberrail' is an anagram of 'IRRITABLE'.
(Other definitions for irritable that I've seen before include "Fractious" , "not very polite" , "cranky" , "Easily annoyed" , "Sensitive" .)