A fine considerably limits current liaison (6)
I believe the answer is:
affair
'liaison' is the definition.
('affair' can be a synonym of 'liaison')
'a fine considerably limits current' is the wordplay.
'a fine' becomes 'af' (I've seen this in other clues).
'considerably' becomes 'far' ('far' can mean 'extremely' or 'considerably').
'limits' means one lot of letters goes inside another (limit can mean to contain or block off).
'current' becomes 'i' (symbol for electric current).
'far' going around 'i' is 'fair'.
'af'+'fair'='AFFAIR'
(Other definitions for affair that I've seen before include "Subject" , "Former Belgian coin" , "Romantic relationship, perhaps illicit" , "Sexual liaison - concern" , "River dam" .)