Devil of a politician leading awful sheepish lot (14)
I believe the answer is:
Here is my best explanation:
'devil' is the definition.
(I have seen 'Senior devil' mean 'mephistopheles' so perhaps 'devil' could also mean 'mephistopheles')
'a politician leading awful sheepish lot' is the subsidiary indication.
'a politician' becomes 'mep' (Member of European Parliament**).
'leading' says to put letters next to each other.
'awful' indicates anagramming the letters.
'sheepishlot' is an anagram of 'histopheles'.
'of' is the link.
(Other definitions for mephistopheles that I've seen before include "Evil demon (Faust)", "Devilish tempter", "diabolical character", "evil character", "Senior devil", "Buyer of Faust's soul" and "Dickens".)