Gutless slugger boxing current holder of title (3)
I believe the answer is:
sir
'holder of title' is the definition.
'sir' can be an answer for 'title' (I've seen this before). I am not sure about the 'holder of' bit.
'gutless slugger boxing current' is the wordplay.
'gutless' suggests removing the centre.
'boxing' indicates putting letters inside ('box' can mean contain, as in to put in a box).
'current' becomes 'i' (symbol for electric current).
'slugger' with its centre taken out is 'sr'.
'sr' going around 'i' is 'SIR'.
Can you help me to learn more?
(Other definitions for sir that I've seen before include "Title of 1 across" , "Poet and novelist" , "Honorary male title" , "Title of knight or baronet" , "Polite or formal address to male" .)