Maybe Lion King not shown in Barrow? (3)
I believe the answer is:
cat
'maybe lion' is the definition.
(lions are big cats)
'king not shown in barrow?' is the wordplay.
'king' becomes 'R' (abbreviation for rex, king in Latin).
'not shown in' is a deletion indicator.
'barrow?' becomes 'cart' (barrow is a kind of cart).
'cart' with 'r' removed is 'CAT'.
(Other definitions for cat that I've seen before include "Sailor's whip with nine knotted strands" , "A tom" , "See 23" , "Domestic animal" , "Feline mammel" .)