Welsh policeman’s heading to seize Coot’s weed (4)
I believe the answer is:
wimp
'weed' is the definition.
Although both the answer and definition are singular nouns, I can't see how they can define each other.
'welsh policeman's heading to seize coot's' is the wordplay.
'heading' says to take the initial letters (head could mean the top letter).
'to seize' indicates putting letters inside.
'coot's' becomes 'I'm' (I am - where the crossword setter is 'Coot').
The initial letters of 'welsh policemans' is 'wp'.
'wp' enclosing 'im' is 'WIMP'.
Can you help me to learn more?
(Other definitions for wimp that I've seen before include "Ineffective type" , "Feeble or ineffectual person" , "Milksop" , "Feeble individual" , "Spineless man" .)