Transport ruminants, about 54 (7)
I believe the answer is:
deliver
'transport' is the definition.
(I've seen this before)
'ruminants about 54' is the wordplay.
'ruminants' becomes 'deer' (deer are a type of ruminant).
'about' means one lot of letters goes inside another.
'54' becomes 'liv' (Roman numerals).
'deer' enclosing 'liv' is 'DELIVER'.
(Other definitions for deliver that I've seen before include "Bring (letters, etc)" , "Supply, hand over" , "ship" , "what the errand boy does" , "The highwayman's cry - 'stand and . . . . . . .'" .)