Most senior English lord is in Paris (6)
I believe the answer is:
eldest
'most senior' is the definition.
(I've seen this in another clue)
'english lord is in paris' is the wordplay.
'english' becomes 'e' (abbreviation).
'lord' becomes 'ld' (abbreviation for the aristocratic title).
'is in paris' becomes 'est' ('is' in French).
'e'+'ld'+'est'='ELDEST'
(Other definitions for eldest that I've seen before include "Most aged" , "Most advanced in age, led set (anag.)" , "Of greatest age" , "Most senior of a group" , "Most old" .)