Nervous journalist, guy losing heart (4)
I believe the answer is:
edgy
'nervous' is the definition.
(synonyms)
'journalist guy losing heart' is the wordplay.
'journalist' becomes 'ed' (short for editor).
'losing heart' suggests removing the centre.
'guy' with its centre taken out is 'gy'.
'ed'+'gy'='EDGY'
(Other definitions for edgy that I've seen before include "Sharp in outline" , "Nervous and tense, irritable" , "Nervous; jumpy" , "ready to flap?" , "Challengingly experimental" .)