Send a great deal in tights (7)
I believe the answer is:
maillot
'tights' is the definition.
(maillot is a kind of tights)
'send a great deal' is the wordplay.
'send' becomes 'mail' (mailing is a kind of sending).
'a great deal' becomes 'lot' (both can mean a large amount).
'mail'+'lot'='MAILLOT'
'in' acts as a link.
(Other definitions for maillot that I've seen before include "Swimsuit" , "Tights worn for ballet" , "Jersey" , "Top" .)