Point out muscle if packing sweaty skin (7)
I believe the answer is:
specify
'point out' is the definition.
(thesaurus)
'muscle if packing sweaty skin' is the wordplay.
'muscle' becomes 'pec' (I've seen this in other clues).
'packing' is an insertion indicator.
'skin' suggests removing the centre (only the skin or outside of the word is used).
'sweaty' with its middle removed is 'sy'.
'pec'+'if'='pecif'
'pecif' inserted into 'sy' is 'SPECIFY'.
(Other definitions for specify that I've seen before include "Mention particularly" , "Spell out" , "Set down as required" , "Identify clearly and definitely" , "State definitely" .)