Pressure on girl at last to consume tuck (5)
I believe the answer is:
pleat
'tuck' is the definition.
(I've seen this before)
'pressure on girl at last to consume' is the wordplay.
'pressure' becomes 'p' (scientific abbreviation).
'on' says to put letters next to each other (in a down clue, letters appear on others).
'at last' indicates one should take the final letters.
'to consume' becomes 'eat' (to consume something is to eat it).
The final letter of 'girl' is 'l'.
'p'+'l'+'eat'='PLEAT'
(Other definitions for pleat that I've seen before include "Fold in material" , "Tuck" , "Gather" , "work on skirt?" , "Fold in clothing" .)