Old ally worried, seeing limits of Tory fidelity (7)
I believe the answer is:
loyalty
'fidelity' is the definition.
(I know that loyalty is a type of fidelity)
'old ally worried seeing limits of tory' is the wordplay.
'old' becomes 'o' (abbreviation as in OT - Old Testament).
'worried' indicates anagramming the letters (worry can mean to interfere with or disturb).
'seeing limits of' says to hollow out the word (remove centre letters).
'tory' with its centre taken out is 'ty'.
'o'+'ally'='oally'
'oally' with letters rearranged gives 'loyal'.
'loyal'+'ty'='LOYALTY'
(Other definitions for loyalty that I've seen before include "Alligiance and fidelity" , "Faithfulness" , "Faithfully allegiance" , "Strong allegiance" , "Fidelity, allegiance" .)