About to follow old German monster (4)
I believe the answer is:
ogre
'monster' is the definition.
('ogre' can be a synonym of 'monster')
'about to follow old german' is the wordplay.
'about' becomes 're' (regarding**).
'to follow' says to put letters next to each other.
'old' becomes 'o' (common abbreviation eg in OE for Old English).
'german' becomes 'g' (abbreviation).
'o'+'g'='og'
're' put after 'og' is 'OGRE'.
(Other definitions for ogre that I've seen before include "One making giant strides" , "Giant of folklore who liked to eat humans" , "Jack's giant perhaps" , "'Demon, fiend (4)'" , "character in 'Puss in Boots'" .)