Relative worried, with expert helping up front (13)
I believe the answer is:
proportionate
'relative' is the definition.
('proportionate' can be similar in meaning to 'relative')
'worried with expert helping up front' is the wordplay.
'worried' becomes 'ate' (I've seen this before).
'with' says to put letters next to each other.
'expert' becomes 'pro' (I've seen this before).
'helping' becomes 'portion' ('portion' can be a synonym of 'helping').
'up front' is a charade indicator (letters next to each other).
'pro' next to 'portion' is 'proportion'.
'ate' put after 'proportion' is 'PROPORTIONATE'.
(Other definitions for proportionate that I've seen before include "in scale" , "Corresponding in size or amount to something else" , "each component should be this!" .)