Deputy loses heart after argument becomes disorderly (5)
I believe the answer is:
rowdy
'disorderly' is the definition.
(similar in meaning)
'deputy loses heart after argument' is the wordplay.
'loses heart' suggests removing the centre.
'after' means one lot of letters go next to another.
'argument' becomes 'row' (to row is to argue).
'deputy' with its centre taken out is 'dy'.
'dy' put after 'row' is 'ROWDY'.
'becomes' acts as a link.
(Other definitions for rowdy that I've seen before include "Uproarious" , "Loud and disorderly" , "Boisterous" , "Raucous" , "Noisy and unruly" .)