Leader sobs uncontrollably (4)
I believe the answer is:
boss
'leader' is the definition.
(I know that boss is a type of leader)
'sobs uncontrollably' is the wordplay.
'uncontrollably' indicates an anagram (I've seen this in other clues).
'sobs' is an anagram of 'BOSS'.
(Other definitions for boss that I've seen before include "Head honcho" , "27 [CHIEF]" , "Stud; chief" , "Team manager" , "Person managing" .)