Welsh Church's plan to secure good deal on energy (9)
I believe the answer is:
charlotte
'welsh church's' is the definition.
(Charlotte Church is a Welsh singer)
'plan to secure good deal on energy' is the wordplay.
'plan' becomes 'chart' (charting is a kind of planning).
'to secure' is an insertion indicator (inserted letters are secured inside).
'good deal' becomes 'lot' (a good deal of something).
'on' says to put letters next to each other (in a down clue, letters appear on others).
'energy' becomes 'e' (physics symbol as in E=mch).
'chart' enclosing 'lot' is 'charlott'.
'charlott'+'e'='CHARLOTTE'
(Other definitions for charlotte that I've seen before include "One of the Bronte sisters" , "Yorkshire novelist" , "... one of the Brontes" , ". . . . . . . . . Bronte wrote ''Jane Eyre''" , "associated with the Web?" .)