Reasons with number of Romans in specs, so to speak (7)
I believe the answer is:
motives
'reasons' is the definition.
(I've seen this in another clue)
'number of romans in specs so to speak' is the wordplay.
I cannot quite see how this works, but
'number' could be 'iv' (IV is an example) and 'iv' is found within the answer.
'of' could be 'o' and 'o' is present in the answer.
This explanation may well be incorrect...
'with' is the link.
(Other definitions for motives that I've seen before include "inducements" , "They're why" , "Reasons for action" .)