Which four gentlemen display pressure? (4)
I believe the answer is:
urge
'pressure?' is the definition.
(I've seen this in another clue)
'which four gentlemen display' is the wordplay.
'display' indicates a hidden word (I've seen 'displaying' mean this).
'URGE' can be found hidden inside 'which four gentlemen'.
(Other definitions for urge that I've seen before include "Strong desire; impel" , "Strong impulse, desire" , "Incite to action" , "Advise strongly to press forward" , "Persuade - proclivity" .)