Clue: Blue tag regularly found in pasture (3)
Answer: LEA
Explanation: Definition: pasture

(b)**L**(u)**E**(t)**A**(g) [*regularly found*]
 

 
I don't like this clue – surely, LEA is found in BLUE TAG. The setter has twisted this around for the purposes of making the surface sound better, but in doing so, he is no longer "saying what he means" as Ximenes would have put it.