Hold cold fish (5)
I believe the answer is:
cling
'hold' is the definition.
(I know that cling is a more specific form of the action grasp)
'cold fish' is the wordplay.
'cold' becomes 'C' (eg on taps).
'fish' becomes 'ling' (ling is a kind of fish).
'c'+'ling'='CLING'
(Other definitions for cling that I've seen before include "Be emotionally over-dependent" , "Hold on tightly, refuse to abandon" , "Hold on as for dear life" , "Hold, cleave" , "fast" .)