Behold old Frenchman appear (4)
I believe the answer is:
loom
'appear' is the definition.
(looming is a kind of appearing)
'behold old frenchman' is the wordplay.
'behold' becomes 'lo'.
'old' becomes 'o' (common abbreviation eg in OE for Old English).
'frenchman' becomes 'm' (abbreviation for Monsieur - like 'Mr').
'lo'+'o'+'m'='LOOM'
(Other definitions for loom that I've seen before include "Bulk large" , "See 12" , "Impend, threaten" , "Apparatus for weaving yarn" , "Impend; weaving machine" .)