Leader of sheep taught under pressure (8)
I believe the answer is:
strained
'under pressure' is the definition.
(I've seen this before)
'leader of sheep taught' is the wordplay.
'leader of' says to take the initial letters.
'taught' becomes 'trained' (training is a kind of teaching).
The initial letter of 'sheep' is 's'.
's'+'trained'='STRAINED'
(Other definitions for strained that I've seen before include "Awkward" , "pushed to the limit?" , "Not relaxed; laboured" , "Filtered" , "Under stress or lacking spontaneity" .)