Old and capacious cups for price (4)
I believe the answer is:
odds
'price' is the definition.
(thesaurus)
'old and capacious cups' is the wordplay.
'old' becomes 'o' (common abbreviation eg in OE for Old English).
'and' means one lot of letters go next to another.
'capacious cups' becomes 'dds' (DD bra size).
'o'+'dds'='ODDS'
'for' acts as a link.
(Other definitions for odds that I've seen before include "Perhaps even money" , "Variance" , "Chance" , "The likelihood of something occurring rather than not" , "Starting price" .)