Understatement in T.S. Eliot play (7)
I believe the answer is:
litotes
'understatement' is the definition.
(I've seen this before)
't s eliot play' is the wordplay.
'play' indicates an anagram.
't'+'s'+'eliot'='tseliot'
'tseliot' with letters rearranged gives 'LITOTES'.
'in' is the link.
(Other definitions for litotes that I've seen before include "Ironic figure of speech" , "not exactly truthful, for example" , "Ironical understatement (grammar)" , "No small task, for example" , "No exaggeration" .)