Underwear, loads of it, is basic stuff (5,5)

I believe the answer is:

brass tacks

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'of it is basic stuff' is the definition.
I can't judge whether this defines the answer.

'underwear loads' is the wordplay.
'underwear' becomes 'bras'.
'loads' becomes 'stacks' (synonyms).
'bras'+'stacks'='BRASS TACKS'

Can you help me to learn more?

(Other definitions for brass tacks that I've seen before include "Nitty-gritty (got down to)" , "Hard facts" , "really mean business" , "Business one gets down to" , "Basics" .)

I've seen this clue in The Irish Times.

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