Head of royal house gathering in money (5)
I believe the answer is:
rhino
'money' is the definition.
(thesaurus)
'head of royal house gathering in' is the wordplay.
'head of' says to take the initial letters.
'house' becomes 'ho' (abbreviation for house).
'gathering' means one lot of letters goes inside another.
The initial letter of 'royal' is 'r'.
'ho' placed around 'in' is 'hino'.
'r'+'hino'='RHINO'
(Other definitions for rhino that I've seen before include "Animal hunted for its horn" , "Large horned mammal" , "In brief, large thick-skinned animal of Africa" , "Beastly type that could charge you" , "Charging animal" .)