British Airways concerns about flatter trunks (7,5)

I believe the answer is:

bathing suits

'trunks' is the definition.
(swimming trunks)

'british airways concerns about flatter' is the wordplay.
'british airways' becomes 'BA'.
'concerns' becomes 'things' (thing is a kind of concern).
'about' means one lot of letters goes inside another.
'flatter' becomes 'suit' (I've seen this in another clue).
'things' placed around 'suit' is 'thingsuits'.
'ba'+'thingsuits'='BATHING SUITS'

I've seen this clue in The Telegraph.

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