Walks nervously heading off with experts (4)
I believe the answer is:
aces
'experts' is the definition.
(ace is a kind of expert)
'walks nervously heading off' is the wordplay.
'walks nervously' becomes 'paces' (I've seen this in another clue).
'heading off' means to remove the first letter.
'paces' with its first letter taken off is 'ACES'.
'with' acts as a link.
(Other definitions for aces that I've seen before include "Playing cards with single pips on their faces" , "passes with flying colours in US" , "Expert fliers" , "wartime pilots?" , "holes in one" .)