Fielder I'm about to send off (3-3)
I believe the answer is:
mid-off
'fielder' is the definition.
(I've seen this before)
'i'm about to send off' is the wordplay.
'about' shows that the letters should be reversed in order.
'to send off' becomes 'doff' (I can't justify this - if you can you should give a lot more credence to this answer).
'im' backwards is 'mi'.
'mi'+'doff'='MID-OFF'
Can you help me to learn more?
(Other definitions for mid-off that I've seen before include "Cricket fielding position" , "Position in the field" , "Someone in field" .)