Tease one bishop after initial reassurance (3)
I believe the answer is:
rib
'tease' is the definition.
(rib can mean to tease or mock)
'one bishop after initial reassurance' is the wordplay.
'one' becomes 'i' (Roman numeral).
'bishop' becomes 'B' (chess abbreviation).
'after' means one lot of letters go next to another.
'initial' suggests taking the first letters.
The first letter of 'reassurance' is 'r'.
'i'+'b'='ib'
'ib' put after 'r' is 'RIB'.
(Other definitions for rib that I've seen before include "spare one?" , "Tease; body part" , "Eve was known as Adam's ..." , "structural member" , "Tease; pectoral bone" .)