Principal support given old woman during visit (8)
I believe the answer is:
mainstay
'principal support' is the definition.
(I've seen this before)
'old woman during visit' is the wordplay.
'old woman' becomes 'ma' (I've seen this in other clues).
'during' becomes 'in' (I've seen this in other clues).
'visit' becomes 'stay' (I've seen this before).
'ma'+'in'+'stay'='MAINSTAY'
'given' is the link.
(Other definitions for mainstay that I've seen before include "Piece of rigging" , "Strong cable that secures a mast, chief support generally" , "big support" , "Pillar of strength" , "Bulwark" .)