Giant pig welcomes dog turning up (7)
I believe the answer is:
goliath
'giant' is the definition.
(giant in the bible)
'pig welcomes dog turning up' is the wordplay.
'pig' becomes 'hog' (synonyms).
'welcomes' indicates putting letters inside (in sense of 'invites in').
'dog' becomes 'tail' (synonyms).
'turning up' is a reversal indicator.
'hog' going around 'tail' is 'htailog'.
'htailog' written backwards gives 'GOLIATH'.
(Other definitions for goliath that I've seen before include "Unusually large person" , "David laid him low with slingshot" , "an unusually tall person" , "Giant David slew" , "Giant Philistine felled by David" .)