Queen wears hat regularly for courage (5)
I believe the answer is:
heart
'courage' is the definition.
(heart is a kind of courage)
'queen wears hat regularly' is the wordplay.
'queen' becomes 'r' (r is abbreviation regina. e.g. in ER ).
'wears' indicates putting letters inside.
'hat regularly' becomes 'heat' (I can't justify this - if you can you should give a lot more credence to this answer).
'r' inserted inside 'heat' is 'HEART'.
'for' is the link.
(Other definitions for heart that I've seen before include "Feeling" , "Kernel" , "Core; organ" , "one in suit" , "Blood-pumping organ" .)