For PM under pressure, computer work takes time (4)
I believe the answer is:
pitt
'for pm' is the definition.
(British Prime Minister William Pitt)
'work takes time' is the wordplay.
'work' becomes 'pit' (pit is a kind of work).
'takes' means one lot of letters go next to another.
'time' becomes 't' (abbreviation).
'pit'+'t'='PITT'
'under pressure computer' acts as a link.
I am not very happy about this link. Some or all of it may be part of another bit of the clue.
Can you help me to learn more?
(Other definitions for pitt that I've seen before include "Youngest-ever British prime minister, d. 1806" , "William - the Younger, twice prime minister" , "William - the Younger, twice PM" , "Brad --, US actor" , "Elder and Younger PMs" .)